Calculating Turn Around Times excluding Sunday

[ls111248]

I need to track turn-around-times, date & time, excluding Sunday. The end
result needs to be the number of dates to completion. In this case the result
should be 4.25.
What I have currently is:
D76 E76 has Formula F76
Date Started Date Completed Number of Days to
Complete
5/12/2010 8:00 AM 5/17/2010 14:00 PM =IF(E76-D76<=0,"",E76-D76)

The formula I'm using does not exclude Sunday. I also receive a #VALUE
error when E76 is empty if I try to add -1 to the formula. (I'm using Excel
2007)

 

[Teethless mama]

A2: Start date
B2: Complete date

=IF(COUNT(A2:B2),SUMPRODUCT(--(WEEKDAY(ROW(INDIRECT(INT(A2)&":"&INT(B2))))>1))-1+MOD(B2,1)-MOD(A2,1),"")