Quarterly Interest Calculating Formula

I use Excel 2007 , I created Interest calculator , on Daily basis , to caluculate interest , compounded quarterly.

But I want to make it compact , as d one I created is long enough.

A3 = Principal Amount
B3 = Date of Investment
C3 = Interest as on Date
D3 = Number of Days , amount Invested {comes out of formula set}
E3 = Rate of Interest

Now in F3 I want the Interest amount , compunded quarterly.

Some times NUMBER OF INVESTED CAN BE LESS THAN 90 DAYS TOO...then what ?