Trying to create a calculated field using groups that have been created summing up General Ledger Accounts (e.g. creating a loss ratio from an account group called Losses and an account group called Sales). I'm stumped
Groups can't be used in calculated fields (though it's on a wish list somewhere). What you'll need to do is create a calculated field that generates the group via either a CASE or IF/THEN statement, and then use that in your calculation.