sqlplus - compute sum of (colA - colB) on report

First and foremost, thanks to all of you for providing and contributing to such a useful resource as this newsgroup.

I am trying to include on a report a grand total of the results of subtracting one column's value from another.

Below is my best effort. Any help will be greatly appreciated.

SPOOL M:\CCMIS\SQL\REPORT_OF_SUBMITTED_BILLINGS.TXT TTITLE 'LIST OF SUBMITTED BILLINGS'
BREAK ON DEL_AGENCY ON REPORT SKIP 2
COMPUTE SUM OF (AMT_BEFOREACCESS - ACCESS_FEE) ON REPORT SET PAGESIZE 60
SET LINESIZE 150
SET NEWPAGE 2
SELECT
DEL_AGENCY,
SITE_NAME,
AMT_BEFOREACCESS - ACCESS_FEE
FROM BILLINGS_HEADER
WHERE MONTH = '02' AND YEAR = '2002' AND SUBMIT_FLAG = 'Y' ORDER BY DEL_AGENCY;
CLEAR COLUMNS
CLEAR BREAKS
CLEAR COMPUTES
TTITLE OFF
SPOOL OFF Thanks again. Received on Thu Mar 21 2002 - 06:14:46 CST