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Is Optional Argument Missing Method

The Is Optional Argument Missing method determines if an optional argument for a procedure is missing. It returns one of the following values:

• -1 (negative one). An optional argument is missing.
• 0 (zero). An optional argument is not missing.

Format

IsMissing(argname)

The following table describes the arguments that you can use with this method.

Example

The following example prints a list of uppercase characters. The user determines the quantity printed. If the user must print every character, then this example calls the myfunc function without any argument. The function uses the Is Optional Argument Missing method to determine to print every uppercase character or to print only the quantity that the user specifies:

Function myfunc(Optional arg1)
   If IsMissing(arg1) = -1 then
      arg1 = 26
   End If
   msgtext = "The letters are: " & Chr$(10)
   For x = 1 to arg1
      msgtext = msgtext & Chr$(x + 64) & Chr$(10)
   Next x
End Function

Sub Button_Click
   Dim arg1
   arg1 = 0
   If arg1 = 0 then
      myfunc()
   Else
      myfunc(arg1)
      End If
End Sub