Why not working onClientPlayerWeaponSwitch?

[Turbe$Z]

function fvalt( prevSlot, newSlot )
	if getElementData (target, "greenzone") then
		setPedWeaponSlot(source,0)
	end
end
addEventHandler ( "onClientPlayerWeaponSwitch", localPlayer, fvalt )

i added this to a greenzones script, but this doesn't working, why?

[AE.]

line number 2 replace target with source or localPlayer