Date calculation formula for Excel?

-I am having trouble working out to enter a formula in Excel.

In column "A" I have a time (eg 13:00)

In column "B" I have a date (eg 13th August 2011)

In column "C" I have another time (eg 17:00)

In column "D" I have another time (eg 17th August 20:11)



I want Excel to be able to work out how many hours it is from the date/time in columns A&B to the date/time in columns C&D. So in column E I want it to say 100.



What formula should I enter ?This should work for you. Format the cell as [h]:mm and enter this formula



=(D1-B1)+(C1-A1)
=SUM(C1,D1)-SUM(A1,B1) format cell as [h]:mm