InfoPath Dev

Hi - I am brand new to InfoPath (which is why I am posting in the shallow end of the pool)  I purchased a book and one of the examples showed how to change the ID field to concat "ID" with the current date/time.   However, after I implemented this, I am getting the error, "Only positive Integers Allowed"   Is this just a bad example and I'm not able to use this type of format for an ID or is there a setting I can change on the ID field to allow this?

Thanks so much!!!!

Fred

 Well - is this a SharePoint list form, perhaps? Or is your ID field's data type set to a Whole Number data type?