multiple sql update w/ major time issues

I have a sql update statement that is dealing with hundreds of
thousands of records. It takes hours and hours to complete (if it
does complete and not take down the server). Here is how I have it
right now:

update aud_member_ext_attributes b
set EXTVALUE217 =
(select a.MTD
from gl_totals a
where a.category = 'tankrent'
and a.CUST_NO = b.EXTVALUE101
and a.DIST_NO = b.EXTVALUE102
and a.SUB_NO = b.EXTVALUE105
and a.FUEL_TYPE = b.EXTVALUE123);

update aud_member_ext_attributes b
set EXTVALUE223 =
(select a.YTD
from gl_totals a
where a.category = 'tankrent'
and a.CUST_NO = b.EXTVALUE101
and a.DIST_NO = b.EXTVALUE102
and a.SUB_NO = b.EXTVALUE105
and a.FUEL_TYPE = b.EXTVALUE123);

update aud_member_ext_attributes b
set EXTVALUE229 =
(select a.R12
from gl_totals a
where a.category = 'tankrent'
and a.CUST_NO = b.EXTVALUE101
and a.DIST_NO = b.EXTVALUE102
and a.SUB_NO = b.EXTVALUE105
and a.FUEL_TYPE = b.EXTVALUE123);

There are 3 "extvaluexxx" that are set for each "category" for a total
of 9 categories. This makes a grand total of 27 update statements.
Any suggestions? It would be much appreciated!!!!!