Option Explicit
' Written by royUK
' [url]www.excel-it.com[/url]
Dim TbCheck
' Assign value.
If TbCheck = IsNumeric(TextBox1) Then
MsgBox "Is not A Number "
Else
MsgBox "Is A number"
End If
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Put this in the Textbox_Change adapt to suit.
I am sure Dave has an article on validating TextBox entries on the main site