VB calculator program

Hi,
Here is my coding for my calculator program in vb..can anyone please help me to modify this coding...here in this coding if i give before number as 12 and click + sign the before will go...but i want tat before number should be on textbox until i give the after number...then if i give after number the after number should display..then if i press equal sign..the addition should take place.

Public Class Form1
Private before As Integer
Private after As Integer
Private symbol As String

Private Sub cmd1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmd1.Click

txtdisp.Text = txtdisp.Text + cmd1.Text


Private Sub cmd2_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmd2.Click

txtdisp.Text = txtdisp.Text + cmd2.Text


End Sub

Private Sub cmd3_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmd3.Click
txtdisp.Text = txtdisp.Text + "3"
End Sub

Private Sub cmd4_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmd4.Click
txtdisp.Text = txtdisp.Text + "4"
End Sub

Private Sub cmd5_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmd5.Click
txtdisp.Text = txtdisp.Text + "5"
End Sub

Private Sub cmd6_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmd6.Click
txtdisp.Text = txtdisp.Text + "6"
End Sub

Private Sub cmd7_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmd7.Click
txtdisp.Text = txtdisp.Text + "7"
End Sub

Private Sub cmd8_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmd8.Click
txtdisp.Text = txtdisp.Text + "8"
End Sub

Private Sub cmd9_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmd9.Click
txtdisp.Text = txtdisp.Text + "9"
End Sub

Private Sub cmd0_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmd0.Click
txtdisp.Text = txtdisp.Text + "0"
End Sub

Private Sub cmdadd_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmdadd.Click
before = Val(txtdisp.Text)
symbol = "+"
txtdisp.Text = " "
End Sub

Private Sub cmdsub_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmdsub.Click
before = Val(txtdisp.Text)
symbol = "-"
txtdisp.Text = " "
End Sub

Private Sub cmdmul_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmdmul.Click
before = Val(txtdisp.Text)
symbol = "*"
txtdisp.Text = " "
End Sub

Private Sub cmddiv_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmddiv.Click
before = Val(txtdisp.Text)
symbol = "/"
txtdisp.Text = " "
End Sub

Private Sub cmdequals_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles cmdequals.Click
after = Val(txtdisp.Text)
If symbol = "+" Then
txtdisp.Text = before + after
End If
If symbol = "-" Then
txtdisp.Text = before - after
End If
If symbol = "*" Then
txtdisp.Text = before * after
End If
If symbol = "/" Then
txtdisp.Text = before / after
End If
End Sub

End Class