I feel rather dumb at not having thought of the suggested solution, which works very well (though I had to amend a little part of it as some parts contain text (of the #N/A ... type)
SUM(IF(ISERROR(B263/C263+B3:B263/C3:C263),0,IF(B263/C263>B3:B263/C3:C263,1,0)))+1
), but in any event the first...