Only display subpages

Hi, I am having a real pain in the ass whit this one hoping you guys can help me out.

I am designing a site for a client, and they want two menus in the sidebar, one for products the have in stock, and one for products they can get.
This is the way the site is set up now:

Home
-Product
–In stock
—In stock #1
—In stock #2
—In stock #3
–Must be ordered
—Must be ordered #1
—Must be ordered #2
—Must be ordered #3

How can I create a list of only sub-pages under a page called “In stock”