What I need to calculate is the duration, in [hh]:mm between the end time of
a shift on one day and the start time of the next shift on another day. Where
this gets complicated, the next start time could be up to 14 days after the
end of the previous shift. How can I write a function to calculate these
total hours?

Ex: Shift 1: 5/1/08 - 17:30 to 05:30 next day
Shift 2: 5/2/08 - 17:30 to 05:30 next day (returns 12:00 for the
duration between shifts)
Shift 3: 5/13/08 05:30 to 17:30 (how do I automatically calculate time
between 5/3/08 05:30 and 5/13/08 05:30 and have this same function calculate
time between 5/2/08 05:30 and 5/2/08 17:30?)

My columns are A(day); B(date); C(Shift [i.e. assigned working shift]);
D(Start Time); E(End Time); F(Duration of Hours Worked); G(Duration of Hours
OFF)

Every day/date is a new row and none are skipped.