As you say, the perimeter more often than not snakes around and is not
an orderly rectangle so the manual process is actually
countblank(range 1)+countblank (range 2) etc until all of the cells
are identified.

I envisage that VB code to do this would involve offseting (2,1) from
start /finish cell. This would identify the first blank cell in the
irregular range that is now surrounded by conceivably up to 8 blank
cells. Getting this far in code and even counting the blank cells
around the offset is no problem for me but then writing code to move
through the range that is bounded by the perimeter of 1's and
identify all of the blank cells is the problem. Yes I think the code
is complex. Its kind of like a search, identify and count mission
where the boundry of the search is a perimeter of ones.

Rosehill