Supplier Backorders

Is there any way to track items on backorder from suppliers in the system? 

For example, with the books I stock. I know I have a quite a few on backorder but when I create the reorder list, they come up to order. I then have to go through manually and cross off the items I have on backorder. I think if I create an unpaid purchase document with the quantities on backorder and save it, it will put those items into my stock. This will then mess up my current on hand inventory.

Can a backorder feature be added if it doesn't exist already?