you can use /target party1 party2 ect for party member healing. or for a more precise way (longer but easier in long run) is to make seperate macros for targeting you healer slave with party members names. easily changed as you join a party it makes targeting easier as the party order list can change if leadership changes ect and it can happen at the same time that party 3 needs a large heal and you press party 3 yet he is now party 4 ect.

also macros that are useful, check the wiki out. sometimes it might seem you have it setup nice then you read a thread and there is a macro on there you like and when you use it you wonder how you lived without it. there is a macro forum on this site or check out the wiki.