Creating a US iTunes account and using it with another on an iPhone...

[Shoot]

I need to redeem a promo code however I live in the uk, I know it's possible to do so but can I use it on my iPhone while still keeping my main account? I think it's possible as I've occasionally logged in on the gf's itouch to install apps and it hasn't stopped her doing stuff with her apps, I just want assurance.

Thanks, shoot

 

[rerelease]

I'm using two accounts with my iPhone, one local and one US. Everything is fine and dandy.