bgp or interface up down script

Hi

I have 4 routers I use to connect to ISP and my main firewall behind them
Current the fw uses a VIP(VRRP) address to use as dgw.

I would like to change the vrrp priority based on if I have my internet BGP peer up. so if 1 of the 4 routers has dropped its BGP peer with the ISP , I would like to set the priority to say 90 and if / when it comes up I would like to set it to 120

possible ?