Different product price for different user access

[guidocx842]

Hi everybody!
I've searched into the forum looking for someone speaking about this feature but I didn't find anything... maybe because I suppose that what you'll read could appear a strange request but, if you think about it, you'll understand that someone could ask you a similar feature for his shop...
I need that the prices of the products change depending on the geographical position of the user that accessing the website.
Simple example: I have a product that coasts 10$ if the user visit the website from USA, 15$ if the user visit the website from Argentina and 20$ if the user visit the website from Europe.
This also if the user is not registered and, if he's registered, the product cost variation have to be independent from the registration information that the user put at the time of registration.
I think a lot on how this feauture can be accomplished and the only thing I thought was that I could use IP address of the user... but I don't know how to proceed and if there is a better way to do this or if exists a Virtuemart extension or trick that do what I need.
Does somebody know something about this?
Thank you very much!!!!