Select Case statements can lead to errors when the test expression in the Select Case line doesn’t yield a true result for any of its individual Case expressions. Therefore, you should always use a Case Else as the final Case within a Select Case statement. This sample raises a custom error when an application invokes the Select Case statement with an operation other than the four basic ones:

 Select Case Operation	Case "Addition"		Computer2 = dblNumber1 + _			dblNumber2	Case "Subtraction"		Computer2 = dblNumber1 - _			dblNumber2	Case "Multiplication"		Computer2 = dblNumber1 * _			dblNumber2	Case "Division"		Computer2 = dblNumber1 / _			dblNumber2	Case Else		Err.Raise 1, , "Wrong operation."End Select