Thanks for your help, but I still don't seem to understand how to do this. I have placed this code on my field that the end-user selects the date. And have named this field givenDate. My other field that I want the date + 90 I have named "Dateafter90". If you could provide a little more help I would...

My form contains a field which the end-user selects a date from a popup calendar. With the date selected I would like to add 90 days to it and post it in another field. Does anyone have an idea how to complete this task? Any help would be appreciated.