partially grading a clip

Hi!

I haven't found an answer to this one yet, so here's my question:

I have a clip with a trumpet player that I want to grade in the latest version of DaVinci Resolve 12 (installed not an hour ago).

I tracked the foremost part of the trumpet, applied the grading to the player as well as to the trumpet, everything works fine. After playing, the trumpet player puts down his trumpet and obviously my grading will end there.

Now my question is: How do I only grade the first part of a clip (when he's playing) and "end" grading for the rest of the clip? I don't want to lose the grading on the player, just the mask for the trumpet should disappear.

Anyone know how to achieve that? Or do I really have to split the clip and apply a transition? That seems a very rough way...

Thanks in advance, best!

Toni