How to setup IK constrains for squats?

Hello,

I have already setup the "Two bone IK constraint" for legs, so that I can walk. Now I would like to make squats, but this is at the moment not possible. I expected, that when I just drag hips down, that the feet and targets would stay on spot so that the player would knee down automatically. But instead, the feet go down, even thought the targets stay on spot:


My question: I guess I need to setup some additional IK constraints also for hips, but I am not sure how to do that. I have searched this in google and youtube, but did not find anything helpful. Does somebody know how to do that?

Thank you
Huxi