Does anyone have experience setting up currency specific subdomains in zen cart?

i.e. depending on the URL the user enters on, the site will default to that locality. Any ideas on how this might be accomplished and or how difficult this might be:

Here's what i was thinking:
www.mydomain.com -> Defaults USD
uk.mydomain.com -> Defualts GBP
ca.mydomain.com -> Defaults CAD
au.mydomain.com -> Defaults AUD
etc...

Thanks in Advance!