Let's take a look at the business process behind the transaction:

When you are ordering that computer from the Supplier, add it to a Purchase Order with drop-ship address information for the customer.  Use the same SKU on the Invoice as you do on the Purchase Order (you can make it non-inventory if that SKU would NEVER be kept in stock).

When you get proof of delivery that the computer has arrived at the customer, then you receive the item against the open Purchase Order and now you a "real time" expense which can be vouchered for payment.  This also allows you to capture freight and other line items which might apply to the drop-ship.

If your business expands rapidly, this would allow you to keep track of your drop-ship activity without re-inventing a separate process.

Kevin