Formula to calculate daily averages

I have an extremely large database with different rows that are transactions during the day. I need to create a formula that will will calculate the daily averages. Here is an example of what my database looks like.

Date Unit Invoice Price
1/1 20
1/1 25
1/1 30
1/2 15
1/2 15
1/2 30
1/3 ....

I want a formula that puts the daily average on the last transaction on each day. So on the third row excluding headings I would like it to say 25 off to the right and on the 6th row 20. Any help would be much appreciated.