Billing per CNAME

Hi All,
I would be interested in hearing how you are actioning the below.

We have multiple CNAME’s (one per project/customer) now we are rolling this out to our wider base we would like to pass the charges onto our customers for the service.

All of the CNAME’s are off the same A record. Is there a way to split out the billing? Or is the only option to have a different A record for each project?

Many thanks in advance.
Regards
Daniel