drop down box on cart

I want to be able to put a drop down box on the shopping cart so it would say.

i would like to give [dropdown] commission on my order.

this would then be added to the email sent to me regarding the order.

It does not have to be in the cart it can be on checkout or anywhere before payment.

also must just say great support thank you very happy so far.

I'm not sure I understand.
You want to add a dropdown on the checkout so that your customers can choose something and then you would see what they selected ?
If that's your question you an do it by creating a custom field of the table "order" via the menu Display->custom fields in the Business edition.