vb高手请进，小弟有个小忙要帮

Command1（0）-Command1（9）为数字键，Command1（10）为小数点，Command1（11）为等号，Command1(12)-Command1(15)为运算符号，Command1（16）为清除。label1为输出结果框。

Option Explicit
Dim Num1, Num2 As Single 'Num1，Num2分别代表输入的第1个数和第2个数
Dim strNum1, strNum2 As String 'strNum1，strNum2分别代表输入的第1个数和第2个数的字符串形式
Dim FirstNum As Boolean '判断输入是否以数字开头
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 = strNum1 + Str(Index)
End If
Label1.Caption = strNum1
Case 10
If Not PointFlag Then
If FirstNum Then
strNum1 = "0."
FirstNum = False
Else
strNum1 = strNum1 + "."
End If
Else
Exit Sub
End If
PointFlag = True
Label1.Caption = strNum1
Case 12 To 15
FirstNum = True
PointFlag = False