Advice to create a little script to associate near shipping address in the next 3 weeks

Hi guys I'm searching an advice on how to proceed to create a script that can calculate the distance between all shipping address in the next 3 weeks and if the distance between some of these locations is under 50 km it must send an email to make that thing notice to the operator. I'm starting from sql 2005 to take location and make all combination. Then I was thinking if there is some online service that, with a link structure where I can put the two location name, can retrieve the distance between those two point, then store it in different variable to use to make comparisons. I'll wait for some advice.thank you guys