Dynamic: Adding up the previous 3 rows from a given cell

Hi guys,

Objective: Track attendance for the past 3 days from today.
MS Excel Version: 2007

Simplified table:

Dates Total no. of Days Present Attendance %
20/01/2014 1 1 100
21/01/2014 2 2 100
22/01/2014 3 2 66
23/01/2014 4 3 75
24/01/2014 5 4 80

To get the % of attendance: =(D3/C3)*100
To get today's date: =TODAY()
To match today's date with Dates column: =INDEX($F$3:$F$19,MATCH($K$7,$B$3:$B$19,1))

All of the above works fine and it returns the Attendance % on that given day.

This is where it gets tricky: how do I ONLY add the two previous days with today's attendance and divide by 3?

The answer that the formula should give is 74% of attendance (e.g. 66+75+80 / 3).

I hope that this makes sense!

Thanks for your time.
Dreamer12.