Adding custom field during checkout

[hues]

I want to add a custom field during checkout only if a particular coupon code is entered.
For example: A customer fills a particular coupon code say FRIE. A text fields should appear which is mandatory to fill some details such as name and address of referrer. For any other coupon code or normal checkout this field is not needed.

This functionality is needed just to track the referrer, as the number of referrers is not fixed.

Is this possible? If yes then please guide me how to do it.
thanks

[dturnertms]

If you are only using the coupon system becasue you want to track the referrer then you might consider writing a programming alteration to:

includes/ templates/template_default/tpl_shopping_cart_default to prompt the user to entering a code and then store this in a new $Session variable. Then if this variable corresponds with a matching known variable (which you are storing in a MySQL table) then you prompt the user for the name+address or whatever info is needed. Again, this gets stored to a MySQL table.

This way you don't need to use the coupon system which you'd need to do programming alterations to anyway to get it to work