Don't know what it's called in Max but in Blender it's the NLA (Non Linear Animation) Editor where you can merge different animations exactly as you describe. Maybe google for that and see what Max comes up with.
Blender's .b3d exporter can even export a new animation based on the merged results. Very cool.
Blender's .b3d exporter can even export a new animation based on the merged results. Very cool.