Finding Averages between various dates

I have a start date in one colum and an end date in another column for a variety of projects.

I also have daily values corresponding to each day for an entire year.

I need somehow to make it so that Excel will take the dates between the start and end date (including the start and end date), and find an average value across all these days with the help of daily corresponding values. I tried using a VLOOKUP function but my success was limited to only managing to get the averages of the start and the end date, and not the average value of all the dates also in between the start and end date.

Thank you!

Didn't work. I'm getting a DIV/0 error. I really dont know what to do, and this is especially difficult because not all projects are the same length (some are 1 day some are 28 days). Anyone got any ideas?

This is what I'm currently using which is not working:

=AVERAGEIFS(C1:C100,B1:B100,">=H2",B1:B100,"<=I2")

where the C column is the value that i want averaged for each day. (600-800 range)

where the B column is the date column corresponding to each C value. (21-Jan-08 format)

where the H column is the beginning date of each project. (same format as above)

where the I column is the end date for each project. (same format as above)

any ideas?

Thank you all very much for your input. DonkeyOte, your formula saved me! Thanks a lot!