Looking good Dave! As you see the Select Case can provide a much cleaner look than the IF THEN in some cases. What you also can do is have a CASE ELSE where you "capture" invalid input (anything BUT + - / *).

You have a lot of Pauses in there that doesn't need to be there if there's no specific reason for it.

Now, since you have the LCD, why not make the messages appear on it instead of the PC-screen? You can still receive the "commands" thru the PC, to begin with.