Average Price With Multiple Date And Prices

Is it possible with 1 formula and avoid to create 300+ individual formulas.

The background info: each day we check the prices of bananas, sometimes we check 2, 3 or 4 times in the same day, and sometimes the price that is checked is the same, but most of the time the price is diferent throughout the day.

We need to know the average dayly price for a particular day, while taking in consideration that some days we have 3 diff prices, and some others we only have 2 or even just 1 price that was checked and thats the price for that day.

we have the following spreadsheet

Column A = Dates
Dates when a price was checked, note here that there might be days of the year when in a single day the price is checked 2 or 3 times, and sometimes the price is different on the same day.

Column B = Price
The price checked on the date indicated in column A

Column C = Daily Avg Price Date
is just a date range from 08/1/11 to 07/31/12, a single day on each cell, that is intended to be the day reference for column D. C1 = 8/1/11, C2 = 8/2/11, C3= 8/3/11 and so on until 7/31/12

Column D = Daily Avg Price
In this column we need to show the average daily price calculated from the prices and dates in columns A and B.

For example: when C1 equals 8/1/11, then D1 has to equal the average price for the product, taking in consideration the amount of prices annotated for that day in column A, with the prices of Column B for that day and providing the average price.

I could have had an easy =Average formula but, since sometimes we have 3 or 2 or 4 equal or different prices in one single day in column A, I dont have a constant for the data range for excel to calculate an average.

My only current solution is to go on each cell on column D and writing the average formula selecting the range that would apply for that average price. But that is taking so much time, and i have multiple other products and year ranges and markets that require this same answer.