debug error

It is not that difficult to debug.

On the line

If Cells(TopRowCtr, TopLastCol - 1) = Cells(SubRowCtr, SubLastCol - 2) And Cells(TopRowCtr, TopLastCol - 2) = Cells(SubRowCtr, SubLastCol - 1) Then

You are setting up the condition so that when "Cells(row,column)" gets evaluated, the column value is either zero(0) or negative. The lowest value allowed is 1.

I recommend learning some basic debugging skills.