What you do is to make a macro to
/equip Brutal Gladiator's Swift Judgement (gives 227 haste-rating)
/cast
/equip Brutal Gladiator's Salvation (gives 500 healing)
haste is calculated when you start casting, healing (or spellower if you are a dps) is calculated when your spell lands.
Edit: According to replies
Since World of Warcraft Client Patch 2.4.3 (2008-07-15) this no longer works on normal spells, but only channelled spells, evocation, tranquillity, arcane missiles etc.
Guess I should have shared it a month or two earlier :-/