Re-create corridor surfaces

Civil 3D
1

I would like to perform soil volume calculations in the following manner.

  1. Edit Subassembly values
  2. Corridor shape is changed in response to 1.
  3. Corridor Surface is created to match the Corridor created in 2.
  4. Calculate soil volume using Corridor Surface in 3.

However, I am now stuck at 3. I have been able to work up to 2 with the attached Dynamo, but have not been able to create a Corridor Surface that matches the Corridor I created.
How can I create a Corridor Surface?
Thank you in advance.
Subassembly_Parameter1.dyn (46.3 KB)
コリドーedit.dwg (1.9 MB)