Time and 3D database

Well I have two problems. The first is the simple one I need excel to take two times in the 24h format and give me the time in tenths. 2106-2200=.9hours.

The second is I want to take the Vspeed charts we have to compute our takeoff vspeeds in an excel spreadsheet. there are elleven altitdues, Sea level and then one through ten thousand feet. Each sheet is broken into two main parameters weight and temperatue. The final conculsion has 4 answers V1, Vr, V2 and takeoff roll. Then I need it to compare between the altitudes, temperatures and weights. It is pretty much a 3D database.

Eric