Different welcome page dependent upon visitors home

I have a cre-loaded online store which I would like to have a different home page / welcome page dependent upon where the visitor comes from. For example if they are from the USA then the page would say something like... Welcome from the USA. You can shop in US Dollars (their currency is variable / look up table to show correct one to the visitor) We ship to USA and we only charge the actual cost of the postage. For example a pair of kitchen scissors would only cost **** to ship to USA. Country codes, currencies etc all pre-programmed in so that the customer feels we are talking direct to him. Don't think it is an enormous job for someone who is good at PHP.