/script DEFAULT_CHAT_FRAME:AddMessage("Need 102.4 combined avoidance. Currently at:",0.8,0.8,1)
/script DEFAULT_CHAT_FRAME:AddMessage(GetDodgeChance()+GetBlockChance() + GetParryChance() +5+(GetCombatRatingBonus(CR_DEFENSE_SKILL) + 20)*0.04,1,0.5,0)
A couple caveats: in "(CR_DEFENSE_SKILL) + 20)", the "20" represents your defense from the Anticipation talent. Adjust accordingly. Also, if you want Holy Shield to be taken into account, you have to turn it on first. This macro was made by Raymond of Nazjatar, so all props to him. I love math.