Definition of internal Wall
 

I want to create a wall in the middle of the two or more blocks.
How may I define a wall between two blocks using BlockMesh dictionary?
If I would be able to define a wall as an obstacle in BlockMesh , it would be very easy for me to define the properties of that wall , in the T , P P_rgh etc.

When I tried to do it with BlockMeshDict it simply said

"Trying to specify a boundary face 4(52 40 64 76) on the face on cell 6 which is either an internal face or already belongs to some other patch. This is face 0 of patch 5 named xyz.