What is wrong with this code??

I made this program that will make sure that only number are put into the txt box. If a letter is put inside of it the program should stop and display me a message. I am using Visual Studio.Net 2003. Here is the code if anyone sees something wrong with it can you let me know? The part in red is what I feel is what is making it go wrong. Right now if you run the application it will add the numbers fine but if you put in a "L" it does not do anything..like display the error message. It has a text box = Purchases and 1 label = tax and 1 label = total. It should do 5.00X.06 that amount should be in the lbltax and then that total should be in the lbltotal. If anyone needs further explanation just ask

Thanks

PrivateSub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btncalc.Click
Dim strpurchase, strpur, strchar AsStringDim intlength, intcount AsIntegerDim blnnonnumberfound AsBooleanDim decpur, decsales, dectotal AsDecimal

strpurchase = txtpur.Text
intlength = strpurchase.Length
blnnonnumberfound = False
If strpurchase = "" Then

MessageBox.Show("Enter an amount as shown above", "5.00")

Else

DoUntil intcount = intlength OrElseNot blnnonnumberfound

strchar = strpurchase.Substring(intcount, 1)

If strchar <> "0" Or "1" Or "2" Or "3" Or "4" Or "5" Or "6" Or "7" Or "8" Or "9" Then

blnnonnumberfound = True

Else

intcount = intcount + 1

EndIf

Loop

If blnnonnumberfound = TrueThen

MessageBox.Show("Invalid purchase amount")

Else

decpur = Val(strpurchase)

decsales = decpur * 0.06

dectotal = decsales + decpur

lbltax.Text = decsales

lbltotal.Text = dectotal

EndIf

EndIf

EndSub

EndClass

Use CASE in Keypress event .....!

In text box keypress event call
keyascii = OnlyNumbers (keyascii)

Fucntion :

Public Function OnlyNumbers(KeyAscii As Integer) As Integer

If (KeyAscii >= 48 And KeyAscii <= 57) Or KeyAscii = 8 Then
FintOnlyNumbers = KeyAscii
Else
FintOnlyNumbers = 0
End If
End Function

Try this its EASY....! Where ever you want to validate pass the KEYASCII

Ooops.. u said that VB.NET....
in the text box keypress pass the keyascci like this


onlynumbers (Asc(e.KeyChar) ' passes the asciivalue

That code would work but I was really trying to keep it like the way i coded it. I am in a call and I can not add things that we have never learned before. I just didn't know if anyone saw this and thought of an explanation on why it may not be working completely for me. Thanks for the contrib though

.NET related questions should be posted in the .NET area.

ok