Opening a Child Window, send URL back

I've been trying to figure out how to do this, but with no luck. I want to do the following:
Open a Child Window. This window will call an swf file that will let the user make various selections and then click on a button in Flash. I'm reasonably certain I can make this work if I know the 2nd part, but I'm definitely not sure about how to do that.

What I want to happen is that when someone clicks on that button, it switches back to the parent window and calls a new URL based on their selections. And without closing the child window.

Can anyone help?

Thanks in advance,

Andy