How to write your own deliveryHandler for Minishop2

Hello,

I am from Barbados in the Caribbean and I need/want write a custom deliveryHandler for my minishop. My island is small and we do not have regions but what we have are parishes. My plan to substitute «parishes» with region. I have started by creating a select box named «region» with the parishes.

<select name="region">
    <option value="Saint Lucy">St. Lucy</option>
    <option value="Saint Peter">St. Peter</option>
    <option value="Saint Andrew">St. Andrew</option>
    <option value="Saint James">St. James</option>
    <option value="Saint Joseph">St. Joseph</option>
    <option value="Saint Thomas">St. Thomas</option>
    <option value="Saint Michael">St. Michael</option>
    <option value="Saint George">St. George</option>
    <option value="Saint John">St. John</option>
    <option value="Saint Philip">St. Philip</option>
    <option value="Christ Church">Christ Church</option>
</select>

There will be 1 delivery option and 2 pickup locations. Once a user selects a «region» for delivery, then the delivery cost is calculated. Here a table to break it down simplier.


I bought mscDistance but it's in Russian and I dont think that it will work for this case. I want to write a delivery handler which can determine the delivery cost calculated from the pickup location (determined by vendor of the product) to the delivery location(region). Any suggestions, code snippets, etc would be appreciated.