adding the following code
For Each TCDraw In TCApp.Drawings
For Each Graphic In TCDraw.Graphics
TCBlock = Graphic.Block
name = TCBlock.name
DumpFile.WriteLine(TCBlock.Name + " used by " + TCDraw.Name)
will show which blocks are used by the various drawings, except if it is in a group.
Coding it for a group is left to reader
This would be a recursive call I will look at it sometime.