SpellCast is a plugin used by FFXI Windower to change gear sets based on actions in game and user preference.
For an example, everytime I use provoke or flash on Paladin SpellCast will change into my Enmity gear for the action and then automatically switch back to my melee or idle gear.
This requires setting up a simple xml file and one macro line in ffxi instead of 1 or more macros dedicated to gear swaps.
If you want to get more out of macros and make life easier in game (less macro mashing) then check it out.
I've created a beastmaster xml and posted it on the site for everyone to look at in awe. I have one for basically every job but haven't fine tuned them all.