Works for me.
I copied the exact code from the help page pasted it into the bottom field on Commerce Setup > Order System > Checkout,
Checked the box "Display Custom Checkout Fields"
Entered "Required to checkout" in the "Text Name" field
Checked the "Req"
Saved changes
Went to the store and put an item in the cart and chose COD for the Payment type.
On billing screen I filled in the billing and shipping info and clicked on Finalize this order.
An error box appeared near the top of the screen with "Please specify a valid value for the
Required to checkout "
I wasn't able to proceed without checking the box.
Try it yourself at :
http://eval.shopsite.com/ssdemos/ver100 ... cials.html
Backoffice login for store is:
http://eval.shopsite.com/cgi-bin/ssdemo ... /start.cgi
User name: alsdemo8
Password: jim
Note the store will only be available for a couple of days so if you are reading this post after Nov 12, 2008 the link won't work.