I am just about to go out for an appointment, but how about this as an
outline.

I am assuming that the data is principally a single block of data, no
complete empty rows or complete empty columns.

Name the top left hand cell  something like "StartCell"

Record a macro  to give you a basic procedure which you can refeine later if
need be.


edit, Goto, select startcell

Hold Ctrl + * to select current Region

Edit, goto, special, blank  cells

That will select all the blank cells in the current region.

In the active cell type the = sign and select the cell immediate above

Press Ctrl + enter  to enter the relative formula into each of the blank
cells.

To polish off, Edit, Goto and select Startcell again.

The resulting macro should give you a good basis to develop further if you
need to.

Let me know how you get on.

I will check the list in the morning.