Found this:
event_off
date/time
The date and time at which the market has actually started (turned in-play). If the market eventually was suspended and turned in-play several times, only the time of the first turning in-play is fixed. If you added the market after it has already started the variable will return the date and time of your adding it to "My Markets". If you added the market after it was suspended and never turned in-play this variable will return zero.
So need to have markets added before they turn inplay, not the end of the world.
When creating conditions, is there any way to use the scheduled off over the actual off, when the market was added to "My Markets" while in play?