Калькулятор двоичной системы счисления

Dim a As String
Dim b As String
Private Sub CommandButton2_Click()
a = TextBox1.Text
 
TextBox2.Text = "-"
TextBox1.Text = ""
 
End Sub
 
Private Sub CommandButton5_Click()
b = TextBox1.Text
 
If TextBox2.Text = "-" Then
TextBox1.Text = a - b
 
End If
End Sub
 
Private Sub CommandButton6_Click()
'очищаем поля
TextBox1.Text = ""
 
End Sub
 
Private Sub CommandButton7_Click()
'вводится 1
TextBox1.Text = TextBox1.Text & "1"
End Sub
 
Private Sub CommandButton8_Click()
'вводится 0
TextBox1.Text = TextBox1.Text & "0"
End Sub

Dim a As String
Dim b As String
 
Function bin2int(b as string) as integer
   if left$(b,1)="-" then
      z%=-1
      b=mid$(b,2)
   else
      z%=1
   end if
   for i%=1 to len(b)
        bin2int=bin2int*2+val(mid$(b,i%,1))
   next i%
   bin2int=z%*bin2int
End function
 
Function int2bin(n as integer) as string
     if n<0 then  z$="-"
     n=abs(n)
     do while(n>0)
          int2bin=Cstr(n mod 2)+int2bin
          n=n\2
     Loop
     int2bin=z & int2bin
End function
 
Dim a As String
Dim b As String
 
Private Sub CommandButton1_Click()
a = TextBox1.Text
 
TextBox2.Text = "+"
TextBox1.Text = ""
End Sub
 
Private Sub CommandButton2_Click()
a = TextBox1.Text
 
TextBox2.Text = "-"
TextBox1.Text = ""
 
End Sub
 
Private Sub CommandButton3_Click()
a = TextBox1.Text
 
TextBox2.Text = "*"
TextBox1.Text = ""
End Sub
 
Private Sub CommandButton4_Click()
a = TextBox1.Text
 
TextBox2.Text = "/"
TextBox1.Text = ""
End Sub
 
Private Sub CommandButton5_Click()
 
    b = TextBox1.Text
 
    If TextBox2.Text = "+" Then
       TextBox1.Text = int2bin(bin2int(a) + bin2int(b)
    End If
 
    If TextBox2.Text = "-" Then
       TextBox1.Text = int2bin(bin2int(a) - bin2int(b)
    End If
 
   If TextBox2.Text = "*" Then
      TextBox1.Text = int2bin(bin2int(a) * bin2int(b)
   End If
 
   If TextBox2.Text = "/" Then
      TextBox1.Text = int2bin(bin2int(a) / bin2int(b)
   End If
 
End Sub
 
Private Sub CommandButton6_Click()
    'очищаем поля
    TextBox1.Text = ""
End Sub
 
Private Sub CommandButton7_Click()
   'вводится 1
   TextBox1.Text = TextBox1.Text & "1"
End Sub
 
Private Sub CommandButton8_Click()
   'вводится 0
   TextBox1.Text = TextBox1.Text & "0"
End Sub