Get a default shipment method shown when filtered by post code

[JacoboPS]

Hello friends,

I am looking for ideas, since I think it is not possible to do what I want to do with the current virtuemart functionality  .

I have a shipment method with a different cost depending on Post Code (and, for a certain post code is not even available, since I don't deliver to those locations). And for this I have as many shipment methods as different post codes (three, in this case).

The thing is, I would like to have one of these shipment methods as the default one, so it is shown on the first screen (I have a one page checkout module), when the user has to register or buy as visitor. And then, on the next screen, when the user enters the form, depending on the post code, show the correct available shipment method for that post code (and not the default one).

Any ideas about how to force a shipment method to appear as default one, when it depends on post code? Or to show a default shipment method not filtered by post code that can be hidden when a post code (any) is entered?

I hope I made myself clear enough  .

(the webpage is www dot 1001especias dot com)