SUMIF 3 variables

Hi

I need to sum (or ideally average) the numbers in column B when teh dates in Column A range between two referenced variables (say 1st Jan and 5th Jan) AND the values in column B are >0 (some are negative numbers).

A B
Order Date Unit price
01-Jan £16.25
01-Jan £4.95
01-Jan -£10.00
04-Jan £35.00
05-Jan £35.00
05-Jan -£10.00
07-Jan £39.25

Date #1 01-Jan
Date #2 05-Jan