Different default currencies for admin and user

[Bersh]

Hello!

I'd like to set up different default currencies for admin and user in my shop. 
For example: when user enter to shop for him default currency should be ukrainian hryvnia, but when admin want to add new product for him default currency should be
united states dollar.

How can I implement this?

P.S. Joomla 1.7.3 + VirtueMart 2.0.8е