Hello guys,

I didn't try the macro but your last formula suggestion fails in some circumstances, I think, NickyC - if A1 is a Thursday at 14:00 and B1 2 days later (a Saturday) also at 14:00 then result should be 16 (4 hours remaining on Thursday and a full day on Friday) but formula gives me 4.

This formula should work for any start/end times/dates and can easily be adapted to exclude holidays too

=12*NETWORKDAYS(A1,B1)-12+IF(NETWORKDAYS(B1,B1),MEDIAN(MOD(B1,1)*24,6,18),18)-MEDIAN(NETWORKDAYS(A1,A1)*MOD(A1,1)*24,6,18)