Just thinking out loud. If you wanted to slow the mouse down then you could hide the mouse, create a mouse sprite and have this sprite move towards the mouses position. I guess you would then have to write your own conditions e.g. if the mouse is clicked then you would have to check what the sprite was over rather than relying on the mouse conditions.
If you wanted it to go faster then I guess (definitely not tested) you could go through loop of remembering where the mouse was compared to when it is and then multiplying this distance by the required amount. You would then need to move the mouse to this new distance and start to loop again. No idea how jerky this would be.
Edit - I wish I could type faster.