Help with join in query

[Scott Pippin]

I have the following query.
 
select
  sum(a.attendhours),
  s.attendhours
from
  attendance a,
  attsum s
where
  a.siteid = s.siteid and
  a.assignmentid = s.assignmentid and
  a.attenddate = s.attenddate and
  a.siteid = 'XXX' and
  a.attenddate >= 'XXXX-XX-XX'
group by
  a.assignmentid,
  a.attenddate;
 
I want it to return those values where sum(a.attendhours) does not equal 
s.attendhours.  What more do I need to add to my query to accomplish this?
 
Thanks in Advance
 
Scott Pippin
[EMAIL PROTECTED]