DataGrid FormatString

Currently I am using the FormatString property in the data grid to convert a decimal to currency value with FormatString="{0:C}", and this works fine except when the decimals are negative. If the value is negative it adds parenthesis around it instead of the negative sign. Usually I would use CultureInfo in the string.Format but I am unsure on what to do here. I understand I could probably achieve my desired behavior via Template but was wondering if I can do the same affect with the FormatString property.

Thank you.