you could make a script or something, figure out how long he does it for, then put the wait just a little shorter than he does it.
something like:
_unit = _this select 0
#start
_unit playmove "FXexecution"
~1 ;change this number so it waits a little before he stops doing the animation
goto "start"
exit
you could also make it so after a certain ammount of seconds it was in teh animation, then it exits the script.