Changing an animation while in motion?

I wanted to setup a system so that if a character in 2D was running, and fired a gun, he would lift his arm and shoot, based on the current frame of the animation.

Would I have to associate each frame to a variable and have it constantly check which variable was active, and then play the animation based on the variable, or would there be a differant want to do this?

You could test for the animation value, which is the current frame, and an alternative would be to separate the torso from the legs and have 2 active objects. I'm sure there are a few ways of doing this.