Is there a way to create a macro for holmgang to function like I have my macros setup for cover as pld?

ex - Healer gets agro I hit my macro and cover joins to him/her

/ac "Cover" <1>

This way so if my healer gets agro I can get pull the target towards me. I was thinking that the players are number <1> , <2> ..... Is there a way to target monsters 1,2,3 in a same manner?

Also if you can't do that I know we have <tt> which is the target of my target. If a healer gets hit with agro does their target switch to their attacker?

I really don't use the mouse over technique yet, if that's the only way I guess I have to start.

ex-

/ac "Holmgang" <t1>