Certificates in Bitrix?

Question

1C-Bitrix

We set the task to make Bitrix certificates.
The administrator can give a certificate for a certain amount for a person, so that this certificate is displayed in the personal account and in the basket. And after partial payment, this certificate should have an amount that has not been spent. And spend this remaining amount in the next purchase.
The question is how to make such a certificate so that it can be personally presented (although this is not the most difficult task)?
The second question is how to make sure that the amount remains?
Why am I asking. Bitrix has coupons for a discount or for an amount, but there is no such thing as setting a rule so that the remaining amount of the coupon does not burn out.
Maybe someone already did this, maybe someone already found the module in the marketplace?