Update Table A To Table B Depending Date Time + ID

need help please on update only if .
i need to update only the field "val_holiday " (in table B from table A)
and olso to check on table B the "ID" + "new_date" only if exist
and update the field "val_holiday " (in table B)


and at the end of update change the field "field_check_update_if _ok" from 0 to 1
only the row that update in table B




Code Snippet
select from table A
update table B
WHERE ..........................HOW ?




----------------------------------------------------------------- table A
ID fname new_date val_holiday field_check_update_if _ok
---------------------------------------------------------------------------------------------------

111 aaaa 15/03/2008 999 0
111 aaaa 16/03/2008 888 0
111 aaaa 18/03/2008 77 0
111 aaaa 19/03/2008 9 0
111 aaaa 20/03/2008 111 0
111 aaaa 21/03/2008 12 0

222 bbb 02/05/2008 15 0
222 bbb 03/05/2008 16 0
222 bbb 04/05/2008 9 0
222 bbb 05/05/2008 3 0
222 bbb 06/05/2008 90 0
222 bbb 07/05/2008 3 0
222 bbb 08/05/2008 3 0
222 bbb 09/05/2008 3 0

333 ccc 03/04/2008 4 0
333 ccc 04/04/2008 4 0


----------------------------------------------------------------- table B
ID fname new_date val_holiday
----------------------------------------------------

111 aaaa 15/03/2008 1
111 aaaa 16/03/2008 1
111 aaaa 18/03/2008 1
111 aaaa 19/03/2008 1
111 aaaa 20/03/2008 1
111 aaaa 21/03/2008 1

222 bbb 02/05/2008 3
222 bbb 03/05/2008 3
222 bbb 04/05/2008 3
222 bbb 05/05/2008 3
222 bbb 06/05/2008 3
222 bbb 07/05/2008 3
222 bbb 08/05/2008 3
222 bbb 09/05/2008 3

333 ccc 03/04/2008 4
333 ccc 04/04/2008 4
------------------------------------------------------------------------------
TNX for the help and for all