I'm trying to figure out if the following is possible. I want to set up my domain so that:

www.mydomain.com --> external photo site (Zenfolio)
blog.mydomain.com --> my blog, hosted elsewhere

To assign my main domain name to Zenfolio, I would modify my domain DNS settings to create an A-record pointing to Zenfolio. So www.mydomain.com would go to my Zenfolio site.

If I did that, I'm trying to figure out how to configure the DNS settings to that I can have a subdomain (blog.mydomain.com) that is hosted separately. It may be that my understanding of DNS is incomplete, but my understanding is that the IP address associated with the A-record handles requests for that domain. I'm just unclear as to how I would configure the subdomain once the A-record is pointing to Zenfolio.

Is what I want to do possible? Can I have two A-records, one for www.mydomain.com pointing to Zenfolio & one for blog.mydomain.com pointing to my web hosting account?

Thanks in advance!
Chris