Problems creating the CNAME record with a subdirectory Wordpress Multisite

Hello,

I have a problem configuring the CNAME record at Cpanel, because I have a subdirectory Multisite.

When I'm adding the CNAME record, it asks me for the name field, right? And you say (at the USAGE page) that in here we have to add the subdirectoy of the user, right?

Would be something like:
mymultisite.com/user-directoy/

But Cpanel is giving me an error, because it says:
..................
Name must be a domain with an optional period at the end.
..................

So... how can I configure the CNAME if I don't have a period at the end?

And also, should I remove the default CNAME that the user has at Cpanel?
I mean the following:
http://www.user-domain.com
14400
IN
CNAME
user-domain.com

Thanks,
Francesco.