Refer a friend campaign to send voucher rather than payout

Hi, I’m looking to create a campaign that will run a ‘refer a friend’ program for me.
After purchase, I’ll create a referral partner and email new customer with referral links. That bit seems straightforward, but I’m stuck on the next part …
If their contact then makes a purchase >£xx, I’d then like to email the original client with a discount code. Any ideas?
Thank you

You could store the original referring person’s info in custom fields on the new contact that was created. Then when the new person makes a purchase send the coupon to the contact info in those custom fields.