sum a column data based on another column data

I am trying to sum a column total bases on an invoiced number column in tsql or ssrs.if I SUM(final) OVER(PARTITION BY InvoiceNmbr) it works fine on all the columns.But once I start to drill down or filter it by office or a user, I only get the total by each user on the invoice and not the cumulative total by the invoice.I want the cumulative total by invoice regardless of which filter I select.any help will be appreciated.