calculating Interest in a month with investments throughout month

[TiChNi]

Certainly there has to be a simplified way to calculate interest owed
at the end of the month when principal was laid out over the course of
several different days during the month and not on consistent days
when looking at it on a month to month basis. Of course I can count
the days for each separate installment of principal but that's totally
manual since the days are not the same each month. So, solve,
demonstrating which function(s) to use, for interest due at the end of
each Nov and Dec if interest was 8% simple.

Principal
11/1/2005 $100.00
11/2/2005
11/3/2005
11/4/2005
11/5/2005
11/6/2005
11/7/2005
11/8/2005 $100.00
11/9/2005
11/10/2005
11/11/2005
11/12/2005
11/13/2005
11/14/2005 $100
11/15/2005
11/16/2005
11/17/2005
11/18/2005
11/19/2005
11/20/2005
11/21/2005
11/22/2005
11/23/2005
11/24/2005
11/25/2005
11/26/2005
11/27/2005 $100
11/28/2005
11/29/2005 $100
11/30/2005
12/1/2005
12/2/2005
12/3/2005
12/4/2005
12/5/2005
12/6/2005
12/7/2005
12/8/2005
12/9/2005
12/10/2005
12/11/2005
12/12/2005
12/13/2005
12/14/2005
12/15/2005 $100
12/16/2005
12/17/2005
12/18/2005
12/19/2005
12/20/2005
12/21/2005
12/22/2005
12/23/2005
12/24/2005 $100
12/25/2005
12/26/2005
12/27/2005
12/28/2005
12/29/2005
12/30/2005
12/31/2005