Path Constraints, Animation & the Curve Editor - Help

[Anaardvark]

Hi, I've got a problem in Max 2011 and wondering if someone might be able to help me?

I've got a series of dots and a curved spline. I've connected the dots to the spline with a path constraint and have animated them to stop at a certain point then carry on after a set number of frames.

However I want the dots to slow down before stopping and then move off slowly and get faster. I've tried to change the tangents in the curve editor but the curve shape doesn't change whatever I try. I can move the keyframe positions but I'm unable to change the shape of the curve.

Does anyone have an idea of what the problem might be?