Make ability to change currency displayed on listings.

Description

We have an auction theme which allows creation of listings. This is a theme from Premium press running on wordpress. To be global we need users to be able to select which currency the item will be listed in. Currently the system allows a base currency to be selected and this then runs throughout the system from listing displayed to invoicing etc. We need the user to be able input the desired currency (we want to give a choice of 3 - GBP, USD or Euro). We do not want to change base currency but have been informed that the way the coding is that everything is connected.
In my mind i think that if the current coding for the icon displayed on the image was disconnected from the system, a new code could be input to allow for the display to show whatever icon gets selected. We are not concerned for the back end to track any of the transactions in their currency or for the invoicing or pay cantre to change as these will remain in GBP and pay centre will change according to the coutry they pay from. We just need a drop down menu of icons to select from and display on the listings accordingly. The input price is just a number.
We have custom field plugin currently being used which maybe able to be used to set the currency field and then tie in to the other areas
The coding is all open source.