How do I use Target Filter?

So, I'm trying to make a tycoon game where I can place down objects wherever I want. I don't want the mouse to target the preview model, and how would I go about doing that? This is what I have so far, and the Target Filter I'm trying to use is in there.

while wait() do
    mouse.TargetFilter = (prevmodel)
    local filter = mouse.TargetFilter(prevmodel)
    if mouse.Target ~= nil then
    if mouse.Target.Parent.Name == "Model" then
    else
        prevmodel:MoveTo(Vector3.new((math.floor(mouse.hit.p.X) +offset),(math.floor(mouse.hit.p.Y) +offset),(math.floor(mouse.hit.p.Z) +offset)))
    end
    end
    if script.TurnOff.Value == true then
        prevmodel:Remove()
        script.TurnOff.Value = false
        script.Disabled = true
    end
end