How to add enter your own amount with orders

I want the customers to to select amount and beable to enter their own amount? I found some solutions in the help area but the form I created does not work?

http://gerlltd.org/index.php/feed-a-horse-program/

Thanks

Hi,

Upon checking it seems you've correctly applied the amount selector box.

Can you please give us more details if there is still a problem on this?

Thanks,