I want to be able to enter a dd/mm/yyyy 00:00:00 format date-time into a MS Excel spreadsheet, add X amount of hours, and return the subsequent dd/mm/yyyy 00:00:00 date-time. This itself I am able to do however it is to be used for telling when a production job will be finished where the factory works shifts Mon-Thu, 6am til 4pm, and 4pm til 2am. I'm not sure how to skip over non-production times.

e.g.
2 hour job starting Thursday 27th Jan 2011 @ 1am would finish Monday 31st Jan 2011 @ 7am. (Production stops at 2am Friday morning after 1 hour of work completed, resumes at 6am the following Monday to carry out 2nd hour of work finishing at 7am.)

Hope this makes sense!!!