Adding rowspans to a table

Hi

I have a three row table where each cell will have a numeric value. I
need to compare values from row[1] and row[2] and rowspan where values
match. I then need to do same for row[2] and row[3].


>From this:
 ______________
|__|__|__|__|__|
|__|__|__|__|__|
|__|__|__|__|__|


To this:

 ______________
|  |__|__|  |__|
|__|  |__|__|  |
|__|__|__|__|__|


I'm sure someone has had to tackle this problem before. Are there any
stylesheets out there that could help me arrive at a solution?

Thanks.

--
Kevin