OT: Different costs for OSPF connected networks through same

I'm trying to make some traffic flow trhough different entry/exit points
in a large L2 network which has a l2l partition.
(I.e. two areas connected by a not so big link, namely two sites
and a l2l link).

Each site has its own GW, both are providing redundant
support to each other. Local addressing has some superimposed L3
networks, some local to each site (logically speaking), some are
"global". They are running HSRP.

Problem: How can I make each router advertise local and remote networks
with different costs so the incoming traffic is routed to the correct
GW ?

-- 
Carlos G Mendioroz  <tron_at_huapi.ba.ar>  LW7 EQI  Argentina
Blogs and organic groups at http://www.ccie.net