Using multi-select property in VBS

Hey guys, I was wondering if anybody could help me out on how to use the "TypedValue.GetValueAsLookups" function.
Here's an explanation on what I want to do.

I have a object called "Shipment", this object has these metadata:
Shipment ID (Integer)
Orders (Multi-select)

And then there's the "Order" object, with the following metadata:
Order ID (Integer)
Product (Text)
Planned shipment (Text)

What I want to do is fill out the metadata "Planned shipment" with the shipment ID everytime a user selects the order from the shipment metadata.
The customer needs this to keep track on which orders that is already has a planned shipment/planned to be shipped.

I have managed to do this with a single select property, but i have no idea how to set this up with a multi-select property.