OK, correction to my last.....not quite so magic, I regret.
I've only just got around to tackling this and have discovered that the suggested method merely populates all cells with the same formula. I need a method that will populate each cell with a formula that adapts to the cell it is in.
I've typed out the formulae by hand for the first three cells (ignore the cell numbers in my first post - this is a fresh example).
Cell a1.....=c38-d37
Cell a2.....=c39-d37
Cell a3.....=c40-d37
I now need to continue that sequence almost four hundred times for cell a4, a5, a6 etc., altering the formulae to c41-d37, c42-d37, c43-d37 etc
Are there any 'quick' ways of continuing those sequences, without typing them all out by hand, please?