Create FaceWall

Importing a mass, getting the surfaces, splitting some surfaces and creating Revit Walls using these surfaces gets stuck on the problem of not having the right references for the split surfaces. Dynamo appears to set for the none split surfaces a tag, that is used in my FaceWall C# code to generate the FaceWall. Is there a way to set the surface.Tags.LookupTag(“RevitFaceReference”) in design script?