Pausing a simple animation

[Jim Biancolo]

[ Sorry if this is a duplicate post - I never saw my original post appear 
on the list, despite seeing lots of other stuff since. ]

Hi folks,

I have a simple animation that fires on mouseUp of a "Play" button:

   repeat for each line L in field "frames"
     set the lockMoves to true
     repeat with i = 1 to the number of images in group "tokens"
       move image i of group "tokens" to ...
     end repeat
     set the lockMoves to false
   end repeat

I know I must be missing something obvious, but I can't figure out how to 
let a "pause" button interrupt this loop.  The "pause" button doesn't 
appear to be clickable until the "play" mouseUp finishes.

Any suggestions would be appreciated!

Thanks,

Jim