Sorry, I should also have made it clear above that a quarter is defined
as the first day in the period to the last day in the period.

Therefore, 1 Jan - 31 March is a complete quarter (for my purposes),
not 1 Jan - 1 April.

I tried the obvious line:

=FLOOR((DATEDIF(STARTCELL,ENDCELL,"M")/3),1

Using the first set of dates, I get 0, and with the second set I get 1

It is close, but not what I actually am trying to do.

Thanks
Neil.