How to Tank/Heal, need focus help plz

I am attempting to tank/heal but am having no luck with it. My heals focus on what the tank focuses on and in order to heal I have to self focus, cast, then tank the mob again. I know it is a simple solution of turning something off in jamba but I'm not sure what it is and am seeking help. Thank you in advance.

[Tin]

With ISBoxer = repeater regions: http://www.dual-boxing.com/showthread.php?t=30511

or you have to make a macro for healing:

/cast [@TankName] Healing spell