Creating mullion from surface

Hello guys,
I’m a grasshopper noob here…
I’m trying to create a mullion and wanted to make the mullion depth as a parameter,
Is it possible for me to offset the lines a divided from the curve and extrude outward based on the surface vector?

Cuz when I try the other way by dividing the surface from the extruded curves, it gives me breps and I can’t divide the surfaces…
Any suggestions? (14.4 KB) Creating_Surface.3dm (9.8 MB) (38.4 KB)