You can use a variable and set it to true when someone starts the mission and false when it ends, when someone wants to start that mission they can only do so if the variable is false
local isMissionStarted = false
addEvent("requestStartMission", true)
addEventHandler("requestStartMission", root,
function()
if not isMissionStarted then
startMision()
else
outputChatBox("Mission not available right now", client, 255, 0, 0)
end
end
)
function startMision()
isMissionStarted = true
end
function stopMision()
isMissionStarted = false
end