Use the Pause/resume script step to pause the script between image changes and your buttons will be responsive between image changes. While the script is paused, your buttons will be responsive. The stop button need not set a variable, it can just perform the Halt script step as this step halts all currently running scripts.
Thanks,... The Pause/resume step did the trick. In fact using that as the delay element (say 5 seconds) times the advancement of photos and I can get rid of the timing loop I set up to perform that function.
For me, the only drawback is I use another script and conditional formatting to cause a fade transition of photos as they are displayed - the tip provided by Jade last week using stepped opacity of an overlay image container. During that transition time (about 2 seconds) in that other script, the cursor changes to the "Cmd - ." symbol, or an hour glass icon if I lock that out via the Allow User Abort script step.
I guess there's no way to deal with the mouse pointer cursor changing icons like that.
Am I correct in assuming there no way to interrupt a running script (except during timed Pause/resume script steps)?
Only command-period (mac) or the escape key (windows) could interrupt the running script and that's something that you have already discovered.