this tile sends you to a zone "x" if you vip , and if you're not sent to another place, as simple as that.
function onStepIn(cid, item, frompos, item2, topos)
local back = {x=1049, y=858, z=15} --Place where non vip is teleported.
local allowed = {x=1025, y=856, z=15} --Place where...