Need help with GPS Coordinate Search

I'm making a website that is for logging Treasure sites, and each site has it own GPS coordinate. Like Site#1 has N34'35.3456 W112'45.2345 coordinate and Site#2 has N35'37.3976 W112'44.2265 coordinate and Site#3 has N33'46.3926 W112'49.2855 coordinate. What I need to do is to make a search for sites, by GPS coordinate, that will show up on a list page, that will list all the sites in a radius of 100 miles or so from the entered coordinate, and will list them from the top being the close to the entered coordinate and getting further away from the entered coordinate at the bottom of the list. I have all my sites in a database. So any Ideas? PS. I really really like the way that Geocaching.com has there GPS coordinate search.

I think this is what I need. I have a database with a column with numbers in it, and I have a dynamic table that will display these numbers and I want to display these numbers by the number that I put in for the query say 6 and the list will list all the numbers starting with 6 in the top row and go down the list with 5 or 7 then 4 or 8 then 3 or 9 and so no. I want the numbers to be displayed with one number higher and one number lower then the number that I put in for the query in a  high and low or a low  and high from the entered number. Like

Row1 = 6 is entered value

Row2 = 5

Row3 = 7

Row4 = 4

Row5 = 8

Row6 = 3

Row7 = 9