Vba Calculator: Click Add After Inputting The Digits Just To Have It Added To He Variable, Which I Just Add Up At The End

i have 1 - 9 number buttons, the +, - , * , / , and a C for clear, as well as an exit button. the display is a label. i have to click add after inputting the digits just to have it added to he variable, which i just add up at the end... terrible.

Option Compare Database
Option Explicit
Dim var1 As String
Dim var2 As String
Dim first As String
Dim second As String
Dim sign As String
' on load
Private Sub form_load()
Form.Caption = "this calculator lab sucks."
Me.lbDisplay.Caption = ""
End Sub
' on clear
Private Sub cmdClear_Click()
Me.lbDisplay.Caption = ""
var1 = ""
var2 = ""
End Sub.............