how to maintian parentheses for the negative values in report

Hi ,

      We like to have the scaling in the reports(Units,Thousasnds,Millions) and in each scaling user also like to have parentheses maintianed for the negative values in the report.

          for Units we have created the Condition and selected the number with Brackets (1234),but for the "Thousands" and "Millions" since we are using cutom , we are nto having this option of parentheses in selection

            Please suggest how to acheive parentheses for negative values for all the scaling values.