Polymorph Macro Help

[Wickedshifts]

I created a small macro for my Mage the other day that looks something like this:

#showtooltip
/focus
/cast Polymorph(Black Cat)
/s %t has been Polymorphed!

This way when I cast polymorph it alerts anyone around me that the target (%t) has been Polymorphed. The only minor thing I have found is that the /s alert is sent at the beginning of the cast instead of at the end when the cast is complete....

Anyone know how I can fix this? (So the /s is announced at the end of a successful spell cast instead of at the beginning?) Thanks is advance