Curtain System by mass

[MrAirport]

I've made a Curtain System on a form element from an imported Conceptual Mass-family. The surface is not curved, but tilted. I then put out grid-lines to divide the panels, and it is importent to be able to control the distances between them. As you can see on the attached image - the angle of the top line on the surface is controlling the grid. How can I set the base line on the surface to make the grid-angle? They are supposed to be horizontal.

I have tried to make the form element in different ways in Conceptual mass, but it doesn't seem to solve my problem.

[Alfredo Medina]

You may want to read this other thread on curtain walls:
http://forums.augi.com/showthread.php?t=122998
There is plenty of good information there that applies to this situation. Scott Davis provided a solution using the intersects feature.