The document discusses measures for tracking foreign currency exposure on a company's balance sheet over time. It proposes calculating: 1) An open invoices measure that sums invoice values filtered by date to show a running total. 2) A year-to-date invoice value measure that cumulatively sums invoice values filtered by date and supplier. 3) A weighting measure that divides the open invoices measure by the year-to-date invoice value measure to show the proportion of the total for each invoice. 4) A weighted exchange rate measure that multiplies the weighting by exchange rates to track how the average rate changes as new invoices are added.