用VB编写计算器？

建立14个按钮，按钮的名字都要Command1，设置Index属性，0~9分别对应数字0~9，10为小数点，11为等号，12~14分别对应+、-、*和/。
2、输入如下代码：
Dim Num1, Num2 As Single
Dim StrNum1, StrNum2 As String
Dim FirstNum As Boolean
Dim PointFlag As Boolean
Dim Runsign As Integer
Dim SignFlag As Boolean
Private Sub Command1_Click(Index As Integer)
Select Case Index
Case 0 To 9
If FirstNum Then
StrNum1 = Str(Index)
FirstNum = False
Else
StrNum1 = LTrim(StrNum1) + LTrim(Str(Index))
End If
Text1.Text = Val(StrNum1)
Case 10
If Not PointFlag Then
If FirstNum Then
StrNum1 = "0."
FirstNum = False
Else
StrNum1 = LTrim(StrNum1) + LTrim(".")
End If
Else
Exit Sub
End If
PointFlag = True
Text1.Text = Val(StrNum1)