[RESOLVED] Need help with code

[Godge]

I'm making a basic calculator program in Visual Basic 6. I have separate text input boxes for the operator and both the numbers for the equation. I've managed to code it so that if the user enters an incorrect character into the operator box, it will open up a message box and alert the user, rather than doing the calculation.

Here's the code I used for the message box alert for the operator input box:

Private Sub cmdCalc_Click()
Select Case txtOperator
    Case "+"
        lblResult = Val(txtNum1) + Val(txtNum2)
    Case "-"
        lblResult = Val(txtNum1) - Val(txtNum2)
    Case "*"
        lblResult = Val(txtNum1) * Val(txtNum2)
    Case "/"
        lblResult = Val(txtNum1) / Val(txtNum2)
    Case Else
        MsgBox ("Operator input error, please use +, -, / or *.")
End Select
End Sub

I want some similar code for the number text input box, so that if the user enters a letter, it opens up a message box in a similar way to the one for the operator. I've tried lots of things but can't seem to get it right. Anyone have any ideas?

Thanks in advance,

Godge.