Okay, I got it to work, if the player has no other augments in their name. If there is anything else in their name this won't work.
Code:
#var autojoin 0
#script {var join_group = new Array()}
#alias {joinon} {#var autojoin 1}
#alias {joinoff} {#var autojoin 0}
#action {( %0 ) %1 is here, fighting %2.} {join_variable;#var {join_target} {$$1};#if {$join_group contains $join_target} {join $join_target}}
#alias {addJoin} {#script join_group.push("$1")}
#alias {join_variable} {#script umc.setVar("join_group", join_group)}
#alias {showJoin} {#script {umc.capture (join_group)}}
#nop -AUTO JOINS-
addJoin Meier
addJoin Apocolypse
addJoin Cashville