Assigning a motion path to CC Light Rays

I'm trying to assign a motion path to the light rays effect on one of my layers but i can't seem to find a way to do it and google has turned up nothing. the problem is the effect needs to be on a certain layer in order to make the effect look right but i don't want the layer to move i only want to affect the centre point of the effect. i can assign key frames and animate it to move in straight lines but i need it to move in a curve and there seems to be no way to alter the motion path or assign it to one on a null layer.

This is driving me crazy so any help would be appreciated.

Thanks