Prevent props from being spawn on spawn platform.

I am working on a lua script & map for my server. I want to stop players from being able to spawn props on the player spawn area.

Here is the function

function ENT:StartTouch( ent )if ply:IsAdmin() then return end	if ( ent:IsValid() and ent:IsPlayer() ) then		self:Remove(prop_physics)		ent:PrintMessage( "Please do not spawn props on the player spawn platform." )	endend

That function is called from a trigger_multiple using an lua_run.

Code = ENT:StartTouch(ACTIVATOR)

This isn’t working, I may have done this completely wrong and I am new to lua.

Any ideas?