how to use user map query to generate a calculated value with MapServer?

[percy]

I would think you would do this through some custom programming using a 
little PostGIS backend query based on rectangle extent and some php to 
iterate through the query results adding up the areas and then dumping 
the summation to an html container in the browser.

but, that's just my approach, someone else might know how to do it 
through mapserver's query mechanism, of which I am no expert.
cheers,
percy

Raymond Fu wrote:
> hi,
>  
> Is it possible and how can I use user map query to generate a 
> calculated value and ?  For example, user draws a recentangle area on 
> the map, the total number of added value of certain field for all the 
> feature within the selected area will be displayed on the browser.
>  
> Thanks
>  
> Raymond
>
> Send instant messages to your online friends 
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-- 
David Percy
Geospatial Data Manager
Geology Department
Portland State University
http://gisgeek.pdx.edu
503-725-3373