if you could, help me figure this out.

I am using aspmailer script to run a form on a page. Here is how it works, someone can write in a form, then in the script is a redirect so that it goes back to that page when they hit submit. I want a pop up window to open when they are pointed back to that page saying their data has been submitted. But I dont want it to happen when they initially arrive at that page? Any help? Would this be javascript? I know some javascript, not alot. If i could do it in the script I would like to do it that way. If no one can help me, tell me where i should post this to get some feedback. thanks!

Josh