cash registery , conversion problem

[ana_eht]

hi everyone
i'm sorry i know i am asking simple questions but i really cannot understand the problem with my code
here i wrote a code for the cash register
( except two buttons : clear and delete )
but it doesn't work
i think something is wrong with the conversions i made
can somebody please tell me what's wrong?!!

Public Class Form1
    Dim num As Double
    Dim Tax As Double
    Dim subtotal As Double = 0


    Private Sub Button7_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn7.Click
        Label1.Text = Label1.Text & "7"
    End Sub

    Private Sub Button9_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn9.Click
        Label1.Text = Label1.Text & "9"
    End Sub

    Private Sub Label2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Label2.Click

    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn1.Click
        Label1.Text = Label1.Text & "1"
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn2.Click
        Label1.Text = Label1.Text & "2"
    End Sub

    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn4.Click
        Label1.Text = Label1.Text & "4"
    End Sub

    Private Sub btn3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn3.Click
        Label1.Text = Label1.Text & "3"
    End Sub

    Private Sub btn5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn5.Click
        Label1.Text = Label1.Text & "5"
    End Sub

    Private Sub btn6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn6.Click
        Label1.Text = Label1.Text & "6"
    End Sub

    Private Sub btn8_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn8.Click
        Label1.Text = Label1.Text & "8"
    End Sub

    Private Sub btn0_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btn0.Click
        Label1.Text = Label1.Text & "0"
    End Sub

    Private Sub btnDot_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnDot.Click
        Label1.Text = Label1.Text & "."
    End Sub
'problem is here
    Private Sub btnEnter_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnEnter.Click
        subtotal = CDbl(txtSubtotal.Text)
        txtSubtotal.Text = CStr(num + subtotal)
        Label1.Text = ""


    End Sub

    Private Sub btnTotal_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnTotal.Click
        num = CInt(Label1.Text)
        If num > 500 Then
            Tax = 0.1 * num
        Else
            If Tax > 100 Then
                Tax = 0.75 * num
            Else
                Tax = 0.05 * num
            End If
        End If
        txtTax.Text = Tax
        txtTotal.Text = Tax + num
    End Sub

    Private Sub btnClear_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnClear.Click

    End Sub

    Private Sub txtSubtotal_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles txtSubtotal.TextChanged


    End Sub
End Class

[GeekByChoiCe]

subtotal = CDbl(txtSubtotal.Text)

i dont see anywhere in your code that u actually set this txtSubtotal.Text before using it.

num = CInt(Label1.Text)

that should be CDbl(Label1.Text)

[ana_eht]

hi
tnx so much
but actually i didnt get what u mean about txtSubtotal.text
should i define it as a variable?!
like :

Dim Subtotal As Double = CDbl (txtSubtotal.Text)

[GeekByChoiCe]

no. i just wonder where this textbox/Label gets its content from. i doubt you want the user to enter the subtotal. but in your code i dont see where you set ever the content of that control. so based on your code the content of this control is NOTHING

[ana_eht]

tnx!!!!!!!!!!!!!!!!!!!!! finally solved it!! tnx so much! yeah ur right i corrected it..!