count unique cells in range based on date

I have a spreadsheet with names in column A and dates in column B, for example:

A(names) B(dates)
Mary 1/1/2007
John 1/1/2007
Joe 1/5/2007
Mary 1/6/2007
Jim 2/1/2007
John 2/1/2007
Joe 2/2/2007

I am planning to do this using named ranges to simplify the function.

I am looking for either a worksheet function or macro that I can use to count the number of unique names, that appear within a specified date range e.g (1/1/2007-2/1/2007). -- In this example: 3 (Mary, John, Joe), I only need the count. I also need the count to display in a single cell in a monthly report (for each month I can show the unique number of people that were active)

So far, I have managed to count unique items in column A using: =SUMPRODUCT(1/COUNTIF(B1:B30,B1:B30))
and count items in the date range: =COUNTIF(A1:A36,">"&DATE(2007,1,1))-COUNTIF(A1:A36,"<"&DATE(2007,2,1))
but I can't figure out how to count the unique items in column A by specifying the date range in column B.

I greatly appreciate any ideas you have.

Thanks.
Dave

I looked thro the forums to find my question, and I'm in the same boat as Dave. I'm trying to count unique entries in column C, and sort them by column A. Column A has 17 different classifications, listed in A2:A19. This was my attempt, but results in the #value error, becuase the second array returns 117 instead of a 1 or 0.

=SUMPRODUCT(--('Calculated Data'!$C$2:$C$10000=A2),--(COUNTIF('Calculated Data'!$C$2:$C$10000,A2)))

Thanks in advance,

`engineers08