Charles is right, there isn't exactly a way to do it, however you can do that work around that he mentioned.
You can set up a subdomain with a domain that is working on the server and redirect that to the new domain that you set up that hasn't propagated yet. Although I don't use the RaQ itself to run DNS, the process should be similar (but with the added DNS steps)...
Set up the new domain on the server.
Set up a subdomain with a domain that is already working on the server. (Make sure that the domain you use is properly DNS'd for the subdomain you are about to create, or wildcarded).
Create the subdomain on the server.
Easy way: Put a simple .htaccess file in the "web" directory of the subdomain you just created that redirects to the domain that hasn't propagated yet. It will work, even though you'd think it wouldn't.
You can now access the site through the subdomain URL you created.
You can access the site's control panel using a combination of the server's IP address (marked below as xxx.xxx.xxx.xxx), and the new domain that hasn't propagated:
Note: You will need to set up a user in the newdomain, and enter the user name and pass here. If you don't know how to set up the .htaccess redirect, just email me and I'll send you a working sample.