Surface/ Loft on Separate Lines

How can I have surfaces on the green lines which are closer together? example between lines 18-19 and 21-22 but no surface between 19-21?

Cone (9.8 KB)

attached is the grasshopper file.

thank you

Like this?

Cone (9.9 KB)

Thank you for your help.

Sorry I am still new to this. What if I want the opposite? The thicker part to have surface while the thinner part to not have surface?

also, why do you graft both A and B for RuleSurface?

Thank you

Cone (9.0 KB)

Yes, you don’t have to graft.