If you don't use an On Error Resume Next statement anywhere in your code, any run-time error that occurs can cause an error message to be displayed and code execution stopped. However, the exact behavior is determined by the host running the code. The host can sometimes opt to handle such errors differently. In some cases, the script debugger may be invoked at the point of the error. In still other cases, there may be no apparent indication that any error occurred because the host does not to notify the user. Again, this is purely a function of how the host handles any errors that occur.
Within any particular procedure, an error is not necessarily fatal as long as error-handling is enabled somewhere along the call stack. If local error-handling is not enabled in a procedure and an error occurs, control is passed back through the call stack until a procedure with error-handling enabled is found and the error is handled at that point. If no procedure in the call stack is found to have error-handling enabled, an error message is displayed at that point and execution stops or the host handles the error as appropriate.
On Error Resume Next causes execution to continue with the statement immediately following the statement that caused the run-time error, or with the statement immediately following the most recent call out of the procedure containing the On Error Resume Next statement. This allows execution to continue despite a run-time error. You can then build the error-handling routine inline within the procedure.
An On Error Resume Next statement becomes inactive when another procedure is called, so you should execute an On Error Resume Next statement in each called routine if you want inline error handling within that routine. When a procedure is exited, the error-handling capability reverts to whatever error-handling was in place before entering the exited procedure.
Use On Error GoTo 0 to disable error handling if you have previously enabled it using On Error Resume Next.
The following example illustrates use of the On Error Resume Next statement:
On Error Resume Next
Err.Raise 6 ' Raise an overflow error.
MsgBox "Error # " & CStr(Err.Number) & " " & Err.Description
Err.Clear ' Clear the error.