Drag & Drop question

Can anyone tell me if such a thing is possible?

I'd like to provide my user a button from which then can Drag a <insert something here> to another window (say an open Notepad document). Once they drop it in that window, my program will grab all of the text in that window and then process it.

Is there any way to let my user drop some code-widget like this?

Thanks

How about just return the hWnd of the window it was dragged on to?