hmmm... nearly got it - this *should* work in theory, but it keeps giving an
error...

=CELL("contents",ADDRESS(ROW()-2,5,4))

if I just put =ADDRESS(ROW()-2,5,4) then it returns a valid cell reference
as text.
if I put =CELL("contents",[validcellreference]) then that also works as
expected. But when I put the 2 together it gives a formula error...

and that's assuming it let's me replace the text with a formula like this...