distance & price script

Hi all i have no clue were to start can some one give me a starting point.
Ok what i need is a script that can handle distance and price.

for example i have 20 towns named A, B, C, D, and so on. i need a function that if you select from town A to town B it will give you a price.

Cheers.

 

i can make you the script.plz send me PM if you want me to do this work for you.