In need of help, please.

I am needing to count the number of attendees of a meeting arriving and departing on separate dates.

Example:

Arrival (column A) Departure (column B)

1/25/2008 2/1/2008
1/25/2008 2/2/2008
1/25/2008 2/1/2008
1/26/2008 2/1/2008
1/25/2008 2/2/2008

If I want to know (count) how many people are arriving on 1/25 AND are departing on 2/1. Or, if I want to know(count) how many people are arriving on 1/25 AND departing on 2/2.

I tried this in my spreadsheet, but got 0 as the result (registered as of 12-5 is the tab name:
=SUMPRODUCT(--('Registered as of 12-5'!U$3:U$424="1/25/2008"),--('Registered as of 12-5'!V$3:V$424="2/1/2008"))

Thanks in advance for your help!!!