Alternatively, if you want to show the user the fomatted text, the MaskedTextBox control with Mask property set as below may be used MaskTextBox1.Mask = "00 - 00 - 00" maskedTextBox1.TextMaskFormat = MaskFormat.IncludePromptAndLiterals string maskedText = maskedTextBox1.Text 'Replace the blank characters maskedText = maskedText.Replace("_","0") The mask characters are explained here http://msdn.microsoft.com/en-us/library/system.windows.forms.maskedtextbox.mask.aspx[^]