There are NP programs that accept applicants with a BS in another area. Check the Nurse Practitioner forum on this site, as I do not know much about these programs and there may be others posting on that forum who are more knowledgable than I am about accelerated NP programs and experience. I do not know of any programs for a MSN with a CNS speciality that are offered without experience as an RN. But that doesnt mean there aren't any out there.
A few web sites you can check out are:
American Academy of Nurse practitioners
www.aanp.org
National Association of Clinical Nurse Specialists
www.nacns.org