Formatting String in Datagrid

I'm trying to format a currency value using the 'dataformatstring' property of a datagrid.

I'm using {0:C} to do this and that's fine to a point. I'm in the UK so it's defaulting to my local culture and displaying £ sign in front of it. Unfortunately some of the currency values I'm dealing with are in US $, also, I it's an editable grid so I'm going to be updating values to the database. I'd like to over ride it in some way to make no currency sign appear.

Any ideas?

"£{0:f2}"