DNS & CNAME Question

editing www cname entry

[jsmart76]

Here is my situation. We have set up a Learning Management System that is being hosted on their servers at a domain, example.com. I would like to have a "brochure" or "welcome mat" website set up on a subdomain i.e. home.example.com which is going to be hosted on separate servers (It is not possible to host them on the same servers). The example.com domain has been set up as an SSL site due to ecommerce that is on it as well. Will this be possible?

I feel like I could simply edit the CNAME record on the example.com servers to have the www alias point to the subdomain, but the LMS company is saying this is not possible.. Any ideas? I just want visitors to be pointed to home.example.com when they go to example.com or www.example.com

At this stage it is not possible to set it up with the LMS on a subdomain and the brochure site as the main URL..