How to set the key frame rate for MS MPEG-4 Video Codec V1/2/3

I am using Microsoft MPEG-4 Video Codec V1/2 to compress live video with
directshow programming. The default key frame interval is 8 seconds. How to
change it programmatically. I tried to use ICOpen and ICConfig set the
interval in its config dialog. But it does not work.

And where can I download Microsoft MPEG-4 Video Codec V3? In my Win XP, I
can only find V1 and V2.