Possible to charge by mile after a certain radius from store?

We would like to be able to charge X per mile after going beyond a 25 mile radius of the store. Possible?

The final formula would be something like:

If distance > 25 {

trueshippingcharge = (costPerMile * 2);

shipping == (trueshippingcharge * (number of miles-25))+65);

} else {

shipping = 65;
}