map vote after every 30minutes

[PorN]

i need a thing for my map script,
i have this atm:
if $MESSAGE = !Ash
/map ctf_Ash
endif

and i want that the command can be only used after 30minutes everytime on that i used it the last time

i hope u know what i mean and i hope that u can help me,
mustn't be a full script

[JFK]

afaik that can not be done with arsse scripting, you'll need a server side script for that