Here is what I posted as a reply yesterday:

You can use the following formulas. Assume that the start time is in

A1 and the end time is in C1.

To calculate the number of hours between start and 6:00:00, use

=MAX(0,TIME(6,0,0)-A1)*24

To calculate the number of hours between 18:00:00 and end time, use

=MAX(0,C1-TIME(18,0,0)+(C1<TIME(18,0,0)))*24

To calculate the number of hours worked between 6:00:00 and 18:00:00,

excluding hours between 18:00 and 6:00:00, use

=(MIN(C1,TIME(18,0,0))-MAX(A1,TIME(6,0,0))+(C1<A1))*24

Cordially,

Chip Pearson

Microsoft Most Valuable Professional

Excel Product Group, 1998 - 2009

Pearson Software Consulting, LLC

www.cpearson.com
(email on web site)