Reference a value from a module but only from selected part of its list
I have a budget that is dimensioned by the complete charter of accounts, so both sales and costs. I'm in another module now where I want to reference the Budget module to get the SUM value of all its costs. If I take the budget line item straight in it will give me the total of both sales+costs, so I basically only want the value of the subset costs list of the Charter of Account list. I know I can create a new budget module based on a subset to get this done easily but isn't there a more sophisticated solution, i.e. a formula that takes care of this without the need for a new module?