how to adjust speed for a limb edit when using an aniblock

Drekkan

What I mean by this is say I load an aniblock of G8F dancing and at one point I want to add a fast kick to the aniblock that she does suddenly which lasts about half a second, while I understand how to edit movements of body parts in an aniblock how do I actually adjust the actual speed of this kick? please try and explain simply.