Adding an extra condition to an IF statement

[Gooford]

=IF(SUM(Q4)=0,"",MAX(0,G4-MAX(F4,Q4))/7) - to calculate number of days for year

=IF(SUM(TODAY()>G4),(G4-MAX(F4,Q4))/7,SUM(TODAY()-MAX(F4,Q4))/7) - to calculate number of days year to date


I am using this condition to calculate the length of a service which falls with in a specific review period, eg

Service starts 1 Feb 09 and finishes 30 April 09

The review period is 1 Mar 09 and finishes 31 May 09.

I would need to measure the number of days that fall within the review period, which would be 1 Mar 09 - 30 April 09

At the moment I am missing a condition which identifies whether to subtract from 'service end date' or 'review end date'.

Difficult to explain, sorry if its not clear, I'll supply further info if needed.

Any help much appreciated thanks