How to check postal code format for user form text box

I'm hoping someone can help! I'm trying to create a data entry form using a userform. I've created a text box for Postal Code. In Canada, the format is A1A 1A1. I would like to validate that the person is entering the postal code in the right format when they are using the user form. I've stumbled on how to do it within the worksheet source code (http://www.excelforum.com/excel-prog...-on-entry.html), but there must be a way to do it when I initialize the user form? I'm using Excel 2010.
Any help??