SW:D Macro question

[Rhylix]

Is there a macro that will refresh (kind of innacurate but best description i can think of) your clients view of your targets hp% to minimize the delay from your target hitting <20% and SW becoming usable? seems to happen in pvp alot, get someone into execute range and they either die or sit there for a second or two and get healed before i can use SW.

I vaguely recall seeing something about this but I don't remember exactly what it was, any help would be appreciated

[purplehazen]

/target player
/targetlasttarget
/cast Shadow Word: Death