Watch out for adding the extra third argument to trigger as show below (which is 1 now). This seems to cause a problem. Was using it in Manipulate and when I added, sometimes the trigger stops firing on its own. When I remove it, it never does stop.
Trigger[Dynamic[t0, {t0 = #} &], {0, 10000, 1}, ....] ToString[#] & /@ a| is same as ToString /@ a