You could make a npc that teleports people in when they click it at a serten time of the day to kick them out at a serten time i think ull have to make it so there is a time limt on the player
first bit would go something like...
[@main]
Hi im the cave npc you can only\
go in @ 6pm intill 7pm\ \
<OK let me in/@oklet>
Exit/@close
[@oklet]
#IF
HOUR 18
MIN 00
#ACT
MAPMOVE 0 200 200
something like that im not doing it all :P