MDI

I've been having trouble with a multiple form (MDI) program. I'm trying to get the second form to return data to the original form and then close. The only time I can get it to work is if I create a new instance of the original form, but that's kind of annoying, because I eventually have a bunch of versions of the same form up. If I don't create a NEW instance of the original form, it comes up with an error message saying that the object reference is not set to an instance of the object.

Any help?