It is rare, but i remember that i used error handler to check if a file exist (that was before i learn more professional way to do that)
Code:
Public Function IsFileExist(ByVal strFileName As String) As Boolean
    Dim dblFileLen As Double

    On Error GoTo FileNotExist
    dblFileLen = FileLen(strFileName)
    IsFileExist = True ' no error occurs, so the file exists.
    Exit Function
FileNotExist:
    IsFileExist = False' an error occurs, so the file not exist.
End Function
Also in some cases if you want to know if the program is running inside the VB IDE or it is running as EXE
Code:
Private Sub Command1_Click()
    On Error GoTo RunInsideIDE
    Debug.Print 0 / 0 ' This line will removed by the compiler when generating the exe.
    MsgBox "The program run as EXE"
    Exit Sub
RunInsideIDE:
    MsgBox "The program run inside the IDE"
End Sub