How do i make a script check when a stat changes then do the following actions when it does?

So I made a leaderstats and a value in it. I want to make a script that checks whenever the value is changed and if u possess certain requirements then it will do the following actions. but my script does not do anything when the value changes

local db = true
game.Players.PlayerAdded:Connect(function(plr)
	wait(5)
	local Leader = plr:WaitForChild("leaderstats")
	local ExpStat = Leader:WaitForChild("Exp")
	local Exp = ExpStat.Value
	ExpStat.Changed:Connect(function(Change)
		local ExpGain = Change - Exp
		if ExpGain > 0 then
			if db then db = false
				Exp = Exp - ExpGain
				wait(0.1)
				Exp = Exp + (ExpGain * 2)
				wait(0.1)
				db = true
			end
		end
	end)
end)

Can you tell me whats wrong because i have no idea