InfoPath Dev

I am in the process of getting familiar with Infopath.  We are migrating from another form generator.  My question is, How can you format data entered into a text field.  For example: you have a SSN field (i.e. 999-99-9999).  In other automated forms, the user can just type the numbers and the numbers will be placed in their proper locations.  Is there a way for infopath do do that?  I know that you can check the field to see if it is entered in the proper format.  But our users are used to entering fields like that without the separators.  Any suggestions would be appreciated.

You can add a rule which uses a substring function to insert the dashes in the correct positions when the cell is left but no I do not believe there is a way to have it build as they go like in some interfaces.