Relatively Complex Geometry

Hello,

I am new using grasshopper and I have a geometry question. I would like merge two geometries together (a square and a circle) and make them so they use a mesh (which is deformed to fit each on different sides) as a tube. Does anyone have any idea of how to achieve this? There is a similar tool in Revit that allows you to define a distinct base and top geometry before completing the extrusion.

Thank you!