private sub Button1_click()
   Text1.Text = Text1.Text & "A"
end Sub
 
private sub Button2_click()
   Text1.Text = Text1.Text & "B"
end Sub
 
private sub Button3_click()
   Text1.Text = Text1.Text & "C"
end Sub
 
private sub Button4_click()
   Text1.Text = Text1.Text & "D"
end Sub