Help with walking

So i’m making server for gmod and i can’t make script.
So basically what i want is when the player has “models/player/police.mdl” this model when he walks he will make this 3 sound effects randomly:
npc/metropolice/gear1.wav
npc/metropolice/gear2.wav
npc/metropolice/gear3.wav
I tried to write this script, but it didn’t worked.


local AllowedModels = {"models/player/police.mdl"}
if !table.HasValue(AllowedModels,ply:GetModel()) then return end
if GM:Move( Player ply )
	then client:EmitSound("npc/metropolice/gear1.wav", "npc/metropolice/gear2.wav", "npc/metropolice/gear3.wav")
end

I know that i’m noob in writing scripts, but can somebody please help me.

This may help you http://forum.facepunch.com/showthread.php?t=1075929
Also

GM:PlayerFootstep