replacing assigned (button) target - how?

I have a simple menu with 2 buttons with text like 'movie1' and 'movie2'. All fine. Now I want to replace one movie file with an updated movie file - everything else should just stay the same. I can't figure how to do that.
If I just drag the new movie file onto the button it covers it and the text is gone/buried/invisible and I can't find anywhere a tool that just let's me 'reselect' the assigned target.

Help very much appreciated!

Oh man, I found the solution. It's 'connect to track' that establishes a new target, then I deleted the other one.....took me hours