Excel 2007 : date,aircraft,time previous 6 months

In my logbook, I have a totals page. What I'm trying to do is to total the flying time in a certain aircraft type for the last 6 months from todays date.
This is my setup:

Column A: DATE. Column B: AIRCRAFT. Column F: TIME.

9/1/10 LJ45 5.0

10/1/10 LJ60 1.9

1/2/11 LJ45 2.0

2/1/11 LJ60 1.9

Thanks for the help.

Jed