Business Discount - online purchase?

How do I make sure I get my business discount when I purchase online?

I generally buy via going to the Apple Store, which is only two blocks from where I live. However sometimes that is not possible (traveling, purchasing late at night). When I am in the store, I give them the name of the company I work for and the discount is applied and shows on my receipt.

The amount saved is not small amount. For example, on a Macbook Pro, I can save $120 with the discount.

So, I am wondering, when I am purchasing through the online Apple Store, where is the ability to get the discount? I looked for a field or check-box, and cannot find one.

Thank you for your time,

Jim