ipsec vpn site to site redundancy with two different links

Hi guys!
i have a problem with ipsec site to site redundant,we have 2 external lines(internet and intranet) we want configure ipsec site to site vpn and redundant with these 2 lines! please help me for configure this scenario?
i configured the ipsec site to site and set the uplink balancing these lines then i set the uplink monitoring for ipsec but we have a problem and a question?! uplink balancing is for 2 same lines but we have one internet link and one intranet???! and if this config is correct so what is not work when i down one link???
Tnx