This Base, Tall and Upper corner fillers that are 90 degrees by default, but can set to varying angles.  There is also an option for setting the right depth different from the left depth, keeping the wall angle in the corner.  It is a simple but very powerful product.  You may need to add two Thickness calculations to your global.  Here are the globals you need to have. 

 Filler_Thickness   Value           =OFFSET(M!Fillers,0,1,1,1)

 Filler_Cleat_Thickness             =OFFSET(M!Cleats,0,1,1,1)