Energy Setting Profiles

Hi, I am quite new in the forum and also in the Apple community. I have recently purchased a MBP with SL updated to 10.6.2. I am trying to set different settings for energy power saving while I am on batteries or mains power and it seems that this does not work for the GPU. I cannot choose the NVIDIA GeForce 9400M while on batteries and the NVIDIA GeForce 9600M GT while on mains power, I can only choose one of them on both occasions. Maybe this topic is already known in the forum but I would appreciate either where in the forum could I point to or what is the solution (if any) for this.

Thanks a lot