Noob: failed attempt to update inner join

Question

I'm attempting to update fields in joined tables bh and bhp, based on information contained in both. The updated fields are not the fields the tables are joined on. I'd expect that to fail but I can't figure out why what I'm trying to do fails. I've read elsewhere in this forum that you can't update views containing joins, and I suspect that's related to this problem, but don't have the experience to understand this better.
I can easily accomplish this update through Access linked by ODBC. What I can't do is write SQL script to do the same. I want to do that so the update can be scheduled with cron.
The tables are logs of having run production batches. batchhistory logs the details of the batch (run time, current status) and batchhistorypatient logs details specific to each affected customer. The tables are joined on batchname, starttime, and facility. The 'last' fields are in both tables but they're not a join field and the distinction is maintained with a fully-qualified field name.
Do I have to create some kind of intermediate view on the fly, and update that?
Thanks in advance for suggestions or referral to specific documentation and examples.
UPDATE HCS.BatchHistory BH INNER JOIN HCS.BatchHistoryCustomer BHC ON
BH.STARTTIME = BHC.STARTTIME AND
BH.BATCHNAME = BHC.BATCHNAME AND
BH.facility = BHC.facility
SET
BH.LAST = "Y",
BHC.LAST = "Y"
WHERE
BH.STATE="COMPLETE" AND
BH.DATEOFSERVICE)<GetDate() AND
BH.last="N" OR
BHC.last="N"
Edited by: Chris Cowles on Feb 16, 2009 11:18 AM. Changed
BHC.LAST = "Y",
BHC.LAST = "Y" to
BH.LAST = "Y",
BHC.LAST = "Y"
Please excuse my error.

Answer 1

Example data:
batchhistory
batchname, starttime, facility, dateofservice, state, last
north, 1/1/2009 0900, abc, 1/1/2009 0830, complete, N
north, 1/2/2009 0900, abc, 1/1/2009 0835, complete, N
north, 1/3/2009 0900, abc, 1/1/2009 0835, complete, Y
batchhistorycustomer
batchname, starttime, facility, customer, dateofservice, state, last
north, 1/1/2009 0900, abc, 0001, 1/1/2009 0830, complete, N
north, 1/1/2009 0900, abc, 0002, 1/1/2009 0830, complete, Y
north, 1/1/2009 0900, abc, 0003, 1/1/2009 0830, complete, Y
north, 1/2/2009 0900, abc, 0001, 1/1/2009 0835, complete, Y
north, 1/2/2009 0900, abc, 0002, 1/1/2009 0835, complete, Y
north, 1/2/2009 0900, abc, 0003, 1/1/2009 0835, complete, N
north, 1/3/2009 0900, abc, 0001, 1/1/2009 0835, complete, N
north, 1/3/2009 0900, abc, 0002, 1/1/2009 0835, complete, Y
north, 1/3/2009 0900, abc, 0003, 1/1/2009 0835, complete, N
batchhistory.last and batchhistorycustomer.last are independent.