calculating fuel economy from a list of purchases

I have a listing of fuel purchase records that I am trying to create a miles per gallon report off of:

The imported file format is something like this:
Column A - Vehicle number
Column B - Transaction date
Column C - Odometer reading
Column D - Gallons purchased

I have been able to sum up the gallons purchased by vehicle number by using a sum if statement. I would like to be able to narrow down the purchased gallons via two cells that I input a start and an end date into, what function or formula could i use to do that?
Im using excel 10, but I would like for the report to be compatible with excel 03 if possible.

The other issue I have not been able to resolve is how to calculate the traveled miles of the vehicle. I know i can use a max and min statement to return the end or start miles, however with my entire fleet of vehicles on one purchase report I do not know how to do this for just one vehicle and still meet the start and ending date criteria. I know this is probably a pretty easy solution for alot of you but I have spent hours trying to find formulas that will do this and I have been unsuccessful.

I have attached a sample file of the problem i am working on. it would be great if on the single vehicle tab I could have the summed gallons, the start and end odometers filled out and possibly a listing of the purchases for the specified unit returned in a range below all of this information. the fleet report tab would just report the summed gallons, start and end odometers, total miles and finally miles per gallon. I would not want any of the source purchase data to display on the fleet tab. any help is very much appreciated, thanks jared