greater equal less than

hi there i am trying to build a calculator for the UK working time directive it requires workers to work no more than 48 hrs a week averaged over a 17 week period as drivers hours vary from day-day week - week i have made a weekly time sheet style spreadsheet which is fine until i get to

if one week they work 56 hrs = 8 hrs above 48 hrs
next week 48 hrs so that is equal to the weekly
3rd week 42 hrs so they have worked less than 48 hrs
etc etc

what kind of formula would be best to work out if above below or equal to the 48 hrs

i'm ok with basic formulas but this has me stumped
thaks in advance if anyone can help

Hi,
how do you define a week?
Mo to Fr, inclusive week ends? How do you take holidays into consideration?