Premiere Pro & Keyframes

[A380]

I'm creating a DVD (motion)menue in Premiere Pro. It is basically a map with an image of a bus that is driving around. I made keyframes for the bus movements.
The bus is now moving slow sometimes and fast the othertimes. How can I make it move at a constant speed? Do I have to set every keyframe at the right position or is there some function that would do the job for me.
Thanks

[kururu]

If you have Premiere Pro 2.0, you can view the velocity in the effect control pallet, just like in AfterFX. Then it's just a matter of moving the keyframes in time to get a constant velocity.

[A380]

I missed that, yes that helps, although it is kind a hard to get a constant speed. Changing one keyframe has effects on the others. Isn't there a "constant speed" function? That would be really cool.