InfoPath Dev

Any suggestions on creating a pattern that will allow any combination of letters or numbers but disallow any special characters.

I have a scenario I would like to be able to design using InfoPath. One area of my data deals with a defined number of events with matrix like data. Ideally I would have two levels of users using the form. The administrator would define how many of the events should occur for this instance of use, and also define a specific set of rows that would ...