I think I have things figured out. I will need to create a cumulative material and dump the results into my Wall Sheathing(1/2" OSB).
Judging from the responses to my post I don't think I explained what I was trying to achieve very well and I apologize. We are building a product where the walls are sheathed using 1-1/2" EPS rigid foam. The first 4' of the wall measured from all outside corners are sheathed with 1/2" OSB and 1" EPS rigid foam to provide racking support. The rest of the walls are braced with metal wind bracing. I am drawing the walls with one wall definitions showing the 1-1/2" foam and I want the software to remove the proper amount of 1-1/2" foam and add the correct amount of 1/2" OSB and 1" EPS.
The outside_corner system variable is the correct one to use but I was approaching it with the concept that I was dealing with two sides of a corner rather than one or two ends of a wall segment. I have to remember that the software is assembling the materials one wall segment at a time. I figured this out by looking at the prepackaged formula for outside siding corners.
When I get this finalized and working I will upload the results.
Thanks for everybody's input.