Helix/Spiral Help

Hey it’s me again. Yesterday, i asked a few questions on attempting to model my physical model on rhino and from the answers i managed to achieve everything i need except for the circular ramp that wraps around the secondary curve. From the picture of the model below, i need the ramp to wrap around the curve starting at the base of the curve and finishing around 2 thirds from the highest point of the curve.

I’ve watched multiple tutorials on ramps and the helix function but i cant seem to get it to work. Any help would be greatly appreciated.
Rhino model for reference
Rhino Model.3dm (232.4 KB)

You might be all done with this by now but in case you still need help…

I’d use Divide to divide the wall edge into three marked segments. Then use InterpCrvOnSrf and draw from an End Osnap to a Point Osnap 2/3 up the divided edge. Lastly, use Fin to make a surface from the resulting curve normal to the wall.