Select Max(Date) from two different tables

This is what I have so far. It is probably way off track, but you will get an idea of what I'm trying to accomplish.

select Max(DatePosted)
from Table1
where customerID = '70'
union all
select Max(DatePosted)
from Table2
where customerID = '70'


What I really want is the Max(DatePosted) from the result of this query (the latest date between the 2 results). I'm new to Sql, so let me know if you need more info.
Thanks

i'm using sql server 2000 btw

select max(v.Date_1) from
( select Max(date_1) as Date_1
from Table1
where id = '70'
union all
select Max(date_1)
from Table2
where id = '70' ) as v


I believe this will works