Restrict Entity based on ULX rank?

I know this has probably been asked a million times before, but I can’t find much on the topic.
I’m trying to restrict an entity to the ULX ‘Donator’ rank. The entity is a Propeller Engine.

Could someone tell me what I would place in the shared.lua file?
I’m somewhat new to LUA and still learning.

Thanks in advance!

Maybe you could hook onto this, and check the usergroup.

Doesn’t look like it would apply much. And besides I don’t know enough to modify it correctly.

How would it not apply?
You check if the entity equals the one you’d block, and then check if the player who tried to spawn it is in the donater usergroup, and if not return false and block it from being spawned.

Would someone be willing to write this for me using the information above?

Why not try this?

I have URS, and I already tried to restrict it with no luck.

[editline]23rd February 2014[/editline]

Update: got it working after doing some reading, thank you for the help.