MaskedEdit in Ajax To0lKit... take a look

MaskedEditExtender is an ASP.NET AJAX extender that attaches to a TextBox control to restrict the kind of text that can be entered. the supported data formats are: Number, Date, Time, and DateTime

MaskedEditValidator is a custom validator which attaches to the MaskedEdit extender and its associated TextBox and verifies that the input text matches the pattern specified in the MaskedEdit extender.

to get more information please take a look at the following link

http://www.asp.net/AJAX/AjaxControlToolkit/Samples/MaskedEdit/MaskedEdit.aspx