Hi
In the example trigger, it is the block named "Executing one trigger after another" which is the one I am suggesting for you. This block is disabled when you download it.
Regarding your question about the second block (enabled as you download it and not the trigger I had in mind for you):
The trigger repeats every 0.3 secs
however, on the first run the timer is not set, therefore:
trigger cancel then lay number of runs is equal to 0 lets the trigger execute first run because the timer variable is not set.
or selections trigger expression (now_time-timer).... the timer variable is set and therefore the timer works correctly on this condition on all subsequent repetitions.
In order to see why what was suggested is not working in your trigger, I need to see your trigger file, or just the basic mechanics of it.