Ok im not that good myself but, you have to make a switch. So its pretty much like this at the end of the event(the point you want it never to repeat at again) place this in the event, Switch Operation and set it to whatever you named the Switch. Then at the top press New Page and in the top left corner it should say Preconditions and check the Switch...is on. So lets see if I can reword this better
Make switch called NameEntry
At end of event place switch NameEntry =ON
Make new page with preconditions set to NameEntry=ON
and set what ever it will do after that.
Now if you want it to do nothing, just leave page2 blank but if it is a person and you want him to say " Hurry before they capture you " or something. anything you want.
Forgot to say. Same thing goes for Chests, just make a new switch and when they get the item from the chest put the Switch Operation event so the switch you made for the chest is ON and on the second page put a message saying " It is empty " or w/e