Ok, i messed up there is more to it, I discovered.
First, place an event, (touch by hero and below hero) in the path of walking for the hero.
Then, open a conditional branch using a switch I call CB (numbering them helps).
Then in branch put the certan event's switch in and to off.
Before End after branch put in the same switch but on.
Now you have half of a one time event.
In the actual one time event, precondition the used switch from the branch.
Then, put in the event data as usual.
Before you put in Proceed with Movement, Erase Event, and End Event Processing put in switch CB to on.
There you have it, the one time vents the way I have found it.
Occasionally, you'll have problems with Move Event and One Time Events. I am still working on it. For now I'll allow others to help fix this problem.