Code event (tracking) to insert

[JoJo!]

Hello everyone,

 

I received a piece of code "event" to insert that will be used each time a coupon code is registered by a customer.
I was given this piece of code

avch ("code", promo_code);
, it is necessary to replace "promo_code" by {$ voucher_code} I imagine.

But should the code be inserted as such or should a function be declared upstream? If so which one please?

Thank you for your help, I'm a bit lost ^^

Good day to all