Constrain to dynamic path

I would like to make a plane move from point to point (empty to empty). How do I stop the plane from leaving the axis created between two empties when the empties are performing an animation? Refer to my image for better clarification.

Thanks

http://img299.imageshack.us/img299/84/dynamicaxisconstraintdf5.th.png

Download the WaoiPoints demo from here:
http://www.neewo.de/Snippets.html

It provides you with one solution to your problem.

Monster