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I want to have an animation loop for a certain number of frames and then stop. I want the same character to do something else. Is there a way I can do this with the loop function?

Search the manual for "faux-fixe".

Thanks that's not quite what I'm looking for.

This is exactly what you're looking for.
Create your looping animation, let's say it's 12 frames long. Extend the last frame to whatever, say 60 frames. Go to frame # 13,right-click, choose faux-fixe and set it to 12, mode repeat. Go to frame # 40 and create a key here. Now play: it loops until # 40 then stops.
This frame (# 40 in my example) is the one where you start with the next animation after the looping part.