VB的小问题请大家帮下首

Dim Num1, Num2, Sum As Double
Dim ACT As Integer

Private Sub cmdDENGYU_Click()
If ACT = 1 Then
Num2 = CDbl(Text1.Text)
Sum = Num1 + Num2
Text1.Text = CStr(Sum)
End If
If ACT = 2 Then
Num2 = CDbl(Text1.Text)
Sum = Num1 - Num2
TRXT1.Text = CStr(Sum)
End If

End Sub

Private Sub cmdJIA_Click()
Num1 = CDbl(Text1.Text)
Text1.Text = ""
Text1.SetFocus
ACT = 1
End Sub

Private Sub CommaJIAN_Click()
Num1 = CDbl(Text1.Text)
Text1.Text = ""
Text1.SetFocus
ACT = 2
End Sub
我编了个计算器.加法就可以无限加.但减法就不行了..为什么??

DIM没定义好

你点完 - 的时候 Text1.Text 就="" 了

再运行 - 时 ,就成了 Num1 - 0 了