how to find bounding county for given long/lat?

[Ravi]

Hi,

I have a situation where given a longitude/latitude, I have to find the 
FIPSSTCO code of the county it is contained in. Now this is not exactly 
reverse geocoding. The information is already there in ESRI shapefiles i 
downloaded. Is there an easy way to do this?

Details: What I am really trying to do is when a user clicks somewhere 
on the map (that gives me longitude/latitude), I want to show a set of 
properties for that county in a table format (which is a simple sql 
query to my database using the FIPSSTCO number). I just need to do the 
conversion.

Thanks for your help
Ravi