Thanks, Michel.
I had considered that, but didn't know if ISY "remembers" X-10 state, sort of as a 'flag/variable'.
For example, if it receives the 'on' message, the rule/folder will be true, since it has not received the 'off' message. It then receives the 'off' message, perhaps 3 days later, so, the folder will not run.
But it then receives the 'on' message a few days later. It has already received the 'off' message, so does it run?
The problem is multiple disconnected 'on' and 'off' X-10 messages, separated by days.
M - send 'on', runs
T - no message, still runs
W - send 'off', so will not run
Th - send 'on', will it run?? it has previously received the 'off' message.
Does the code you suggested mean: When you receive an 'on' message, the folder is activated for 'running', until a later 'off' message is received, at which point it will stop running, until another 'on' message is received, at which point the cycle restarts.
Thanks, Frank.