I've done a bit of searching on this topic looking for my exact situation but have not found this exact flavor.
I have example.com and use DreamHost as my registrar. example.com, for the time being, needs to point somewhere else (another web host). I want to set up beta.example.com with hosting on DreamHost.
So I have the domain set up with its nameservers pointing elsewhere, and attempts to set up beta.example.com. What do I need to do to get beta.example.com working?
My working theory is that I need to switch example.com's nameservers back to DreamHost's DNS and then adjust the A records for the top-level stuff so that it points elsewhere. But I'm not sure if this will work, as DreamHost creates uneditable A records for sites "hosted" on it.
*Sorry that this so wordy.