CNAME editing/setup

[Silverado]

I have a client using a "website builder"... the subdomain must be set up with a CNAME to the web site offering the software.
The subdomain already has an "A" entry and my WHM is not letting me create a CNAME entry for this subdomain to point to the other server as required.
This is the error message I receive:
sitebuilder 14400 IN A domain.com.

near 'domain.com.': bad dotted quad 14400 IN A near '': bad dotted quad

Do I need to delete the "A" entries for this domain first before I change/create/edit the zones for the CNAME entry?

Thank you.

[Silverado]

Just an update for anyone else that runs into this problem..... the "A" entries must be remove and ONLY a CNAME entry for
subdomain and www.subdomain needs to be entered.
I hope this helps someone in the future. It was exactly what we had to do for the subdomain to resolve to another server.