Help with custom shipping module

I am trying to do a custom shipping calculator for my country but I have no clue where to start.All modules I see are from US,Europe or some other major country.I am from the Caribbean and I want to have one on my sit specifically for my island as I don't ship internationally.Are there any module I can edit to help me.The company that ships for me is only local to my country and they their shipping calculator on their site show the following

<td class="B2"><div align="right">Select Pick up 
                                Point:</div></td>
                              <td><select size=1 name=begin>
                                  <option 
                                value=0 selected>Please Select</option>
                                  <option value="800">Aberdeen</option>

                                  <option 
                                value=800>Adelphi</option>
                                  <option value="1300">Albert Town</option>
                                  <option value="800">Alexandria</option>
                                  <option value="800">Alligator Pond</option>
                                  <option value="800">Anchovy Portland</option>
                                  <option value="800">Anchovy St. James</option>

                                  <option value="672">Annotto Bay</option>
                                  <option value="622">Azan Tours</option>
                                  <option value="800">Balaclava</option>
                                  <option value="800">Berrydale</option>
                                  <option value="800">Berrydale</option>
                                  <option value="800">BethelTown</option>

                                  <option value="672">Black River</option>
                                  <option value="800">Bluefileds</option>

What this does is show a different shipping for different districts and towns in my island.
Can someone point me in the right direction?
This just have a few of the towns and districts.There are a lot more to add but I just need a start.