(Please note that I've worked around the issue below by changing every cell
manually, so this isn't an urgent request - but I imangine I may need a
better answer in future, and it's possible other people might also be
grateful if anyone has a solution.)

I have a block of cells containing a variety of unrelated formulae. I want
to change one element of each formula from a relative to an absolute
reference.

I tried highlighting all the cells, clicking in the formula bar and pressing
f4 (three times, to make column reference absolute and leave the row
reference relative) but this changes only the first cell in the block.

If the formulae were in sequence I could change one and copy it to the other
cells, but since they are all different that won't work. Does anyone know how
to change the references throughout a selecteed group of cells?