Is there a way to provide a discount code that someone can enter when checking out?

You can create a discount/coupon code for any program.  

• Go to Programs > Manage Programs.
• Click on the program name.
• Go to the 2 Configuration page.  
• Scroll down to the bottom and click the Add Coupon button.  
• Go to the help page for specific information related to the Coupon Codes.