Error Handling In Excel 2003
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three flavors: compiler errors such as undeclared variables that prevent your code from compiling; user data entry error such as a user entering a negative value where only a positive number is acceptable; and run time errors, that occur when VBA cannot correctly execute a program statement. error handling excel vba We will concern ourselves here only with run time errors. Typical run time errors include attempting
Error Handling In Excel Formula
to access a non-existent worksheet or workbook, or attempting to divide by zero. The example code in this article will use the division by zero error handling in excel macro error (Error 11) when we want to deliberately raise an error. Your application should make as many checks as possible during initialization to ensure that run time errors do not occur later. In Excel, this includes ensuring that required workbooks and worksheets
Excel Error Handling #n/a
are present and that required names are defined. The more checking you do before the real work of your application begins, the more stable your application will be. It is far better to detect potential error situations when your application starts up before data is change than to wait until later to encounter an error situation. If you have no error handling code and a run time error occurs, VBA will display its standard run time error dialog box. While this may be excel error handling #value acceptable, even desirable, in a development environment, it is not acceptable to the end user in a production environment. The goal of well designed error handling code is to anticipate potential errors, and correct them at run time or to terminate code execution in a controlled, graceful method. Your goal should be to prevent unhandled errors from arising. A note on terminology: Throughout this article, the term procedure should be taken to mean a Sub, Function, or Property procedure, and the term exit statement should be taken to mean Exit Sub, Exit Function, or Exit Property. The term end statement should be taken to mean End Sub , End Function, End Property, or just End. The On Error Statement The heart of error handling in VBA is the On Error statement. This statement instructs VBA what to do when an run time error is encountered. The On Error statement takes three forms. On Error Goto 0 On Error Resume Next On Error Goto
the wrong time. The application may crash. A calculation may produce unexpected results, etc. You can predict some
Excel Vba Error Handling Best Practice
of these effects and take appropriate actions. Some other problems are not
Excel Vba Error Handling In Loop
under your control. Fortunately, both Microsoft Excel and the VBA language provide various tools or means of excel vba error handling type mismatch dealing with errors. Practical Learning:Introducing Error Handling Open the Georgetown Dry Cleaning Services1 spreadsheet and click the Employees tab Click the Payroll tab Click the TimeSheet tab To http://www.cpearson.com/excel/errorhandling.htm save the workbook and prepare it for code, press F12 Specify the folder as (My) Documents In the Save As Type combo box, select Excel Macro-Enabled Workbook Click Save Introduction to Handling Errors To deal with errors in your code, the Visual Basic language provides various techniques. One way you can do this is to prepare your code http://www.functionx.com/vbaexcel/Lesson26.htm for errors. When an error occurs, you would present a message to the user to make him/her aware of the issue (the error). To prepare a message, you create a section of code in the procedure where the error would occur. To start that section, you create a label. Here is an example: Private Sub cmdCalculate_Click() ThereWasBadCalculation: End Sub After (under) the label, you can specify your message. Most of the time, you formulate the message using a message box. Here is an example: Private Sub cmdCalculate_Click() ThereWasBadCalculation: MsgBox "There was a problem when performing the calculation" End Sub If you simply create a label and its message like this, its section would always execute: Private Sub cmdCalculate_Click() Dim HourlySalary As Double, WeeklyTime As Double Dim WeeklySalary As Double ' One of these two lines could produce an error, such as ' if the user types an invalid number HourlySalary = CDbl(txtHourlySalary) WeeklyTime = CDbl(txtWeeklyTime) ' If there was an error, the flow would jump to the label WeeklySalary = HourlySalary *
expression) returns an error, and if so, returns a second supplied argument; Otherwise the function returns the initial value.Note: the Iferror function is new to Excel 2007, so is not available in earlier versions of Excel.The syntax of the function is:IFERROR( value, value_if_error )Where the arguments are http://www.excelfunctions.net/Excel-Iferror.html as follows:value-The initial value or expression that should be testedvalue_if_error-The value or expression to be returned if the supplied value argument returns an error.Iferror Function Example 1The following spreadsheet shows two simple examples of the Excel http://www.fmsinc.com/tpapers/vbacode/Debug.asp Iferror function.Formulas:ABC112=IFERROR( A1 / B1, 0 )210=IFERROR( A2 / B2, 0 )Results:ABC1120.5 - A1 / B1 produces no error so result 0.5 is returned2100 - A2 / B2 produces an error so the alternative value 0 error handling is returnedNote that:In the first example (in cell C1), the value argument, A1/B1 returns the value 0.5. This is not an error and so this value is returned by the Iferror function.In the second example (in cell C2), the value argument, A2/B2 returns the DIV/0! error. Therefore, the Iferror function returns the value_if_error argument, which is 0.Iferror and Vlookup - Improvement Compared to Excel 2003The Excel Iferror function was introduced in error handling in Excel 2007.Previously, in Excel 2003, many users of the Excel Vlookup function would combine this with the If function and the Iserror function, to test for an error, and return an appropriate result. This is shown in the following formula:IF( ISERROR( VLOOKUP( ... ) ), "not found", VLOOKUP( ... ) )the above formula checks if the Vlookup function returns an error, and if so, returns the text "not found". Otherwise the value returned by the Vlookup is returned.Although this formula is long and inefficient (as it requires 2 separate calls to the Vlookup function), it is useful because it helps to keep your spreadsheet cells tidy and free from error messages.In Excel 2007 (and later versions of Excel), the above action can be performed much more efficiently and neatly, by using the Iferror function. The new formula is written as:IFERROR( VLOOKUP( ... ), "not found" )An example of this is provided below.Iferror Function Example 2The following spreadsheet shows two further examples of the Excel Iferror function. The formulas are shown in the top spreadsheet and the results are shown in the spreadsheet below.Formulas:ABCD1Lookup ListJim's Class:=IFERROR( VLOOKUP( "Jim", A2:B6, 2, FALSE ), "not found" )2BethClass 1Mary's Class:=IFERROR( VLOOKUP( "Mary", A2:B6, 2, FALSE ), "not found" )3BobClass 24AlfClass 25JimClass 36AnnClass 3Results:ABCD1Lookup ListJim's Class:Class 32BethClass 1Mary'
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