Using shadow replacement to create a hold out matte


I am the proud new owner of Monet (and Mokey) and am working on a hand-held shot where a street sign is being replaced with a new sign. This part works just fine. However, at one end of the clip, a tree partially obscures the sign. I was impressed with the way Monet can replace highlights and shadows from an original item over the top of the replacement item. I wondered if it is possible to use this to create a hold out matte for the tree. I was able to use the method as advertised to create a shadow version of the part of the tree covering the sign using luminance and reference frames. This creates what looks very like a hold out matte but is not used in that way. Is there a way to use it as a hold out matte within Monet? It seems it’s so close to being able to do this - like I just need to multiply it with the new image some how. Your help would be greatly appreciated. I really want to learn all the matting capabilities of Monet.