How to access wall core faces

How do you access wall core faces? My aim is to create a horizontal line and select vertical walls in plan, and dimension them from core to core (the layer between Core Boundaries).

I discussed this with Petar_Penchev1 after reading Automatic Dimension Walls this topic, he suggested to create a new topic and ask around. Couldn’t find similar topic, so if asked before sorry to bother.

Hello,

That is on the Revit Ideas wish list. You should go there and wrote http://forums.autodesk.com/t5/revit-ideas/api-to-get-references-to-wall-center-core-center-core-faces-for/idi-p/6641794

Did that. Thank you very much.