PW:S and Mouse problems

I'm setting up my Priest to heal my DK team and I've run into a minor snag.

I have my Spacebar button send F9, Shift+F9, Alt+F9 etc (6 buttons in all) to every window. On my Priest I have 5 macros--each one casts PW:S on a different toon. The idea is that as I'm spamming my DPS key my Priest will try and put Shield up on each guy every time it's available.

My problem is this:

As I spam it, if it can't cast the spell on them due to the Weakened Soul debuff, it puts the PW:S on my mouse. Meaning, my mouse changes to have the blue outline and will cast the PW:S on the next person I target.

I need either an API function that will remove it from my mouse, or an option in game/UI addon that will prevent/remove this. Or, I guess, a completely other way to keep PW:S up on 5 guys with one button that ISN'T a castsequence--I want to be 100% certain it's hitting them and I don't want it snagging up due to lag or my ping or whatever.

http://www.dual-boxing.com/showthread.php?t=33669


Power Word: Shield was the specific reason for wanting to do this.
But it will be useful for Rejuvenation, or anything like that as well.

That was my backup solution to the problem--I was hoping for something that isn't based off of my latency. I did, however, set it up and I'm still getting the spell on my cursor when I spam my DPS button.

Ok, found a way that totally works with a spam button:

/target Chervabog
/cast Power Word: Shield
/targetlastenemy

And then 5 buttons each with a different character name. The problem is that the macro lags my main. A single macro makes him stutter every time I press it. Multiples makes it nigh-unplayable.

Any help?

Fixed:

For whatever reason, I had to change which buttons in ISBoxer were sent to my Priest when I hit my spam button. It fixed it.