I am trying to subtract the time that an action will take from a target date. For example: Cell D2 has the date and time 10/30/13 08:00. I want to use a Workday formula to subtract 4 hours from that which should give me the value 10/29/13 13:00. Is there any way to manipulate the Workday formula to achieve this?

Also, can I adjust what hours are in my workday?