Not sure you would do anything like this at all when the smartbuff mod exists. You configure it once for each character that can cast buffs, then bind a single key to it, and you can then spam that key and it will auto-buff your entire party as you have it configured. You can make this the same key for all your characters and then just spam that key to rebuff your entire party - way easier and much more foolproof then a macro. You can even configure which buffs you want to allow in-combat in case you need to rebuff only high priority buffs in combat, etc. It even works for self buffs like watershield, etc.