How to do changed event?

I'm not entirely sure how to use the changed event, but I made this script to make a sound and change a decal's transparency when a value is changed. Here's the script:

function warp(value)
	script.Parent.Parent.db = false
	game.Workspace.StarshipWiz.Helm.Part.warp1:Play()
	game.Workspace.StarshipWiz.warp.Decal.Transparency = 0
	wait(12)
	script.Parent.Parent.db = true
	game.Workspace.StarshipWiz.Helm.Part.warp2:Play()
	game.Workspace.StarshipWiz.warp.Decal.Transparency = 1
end

game.Workspace.StarshipWiz.Planet.Changed(warp)

The output says, "Workspace.StarshipWiz.Planet.Script:11: attempt to call field 'Changed' (a userdata value)"

Can someone tell me how to rectify this?