Help with DNS error messages

[Funwithme]

I have a webhosting company IX webhosting.com and they host several of my 
sites. They are about to relocate all the sites to a new physical location 
and naturally they didn't plan well enough to make sure the sites stay 
visible and so this weekend all the sites will crash.  What I want to do is 
try to get them to setup a page on a remote server that simply hosts the 
error pages.  Instead of the idiotic HTML404 error page I want them to post 
a page that simply tells what is happening and that customers can try again 
in 2 or 3 days.  Naturally their management console allows me to create 
custom error pages but those will be unavailbale as well as the site so that 
is not a solution.  I am wanting them to designate a location that serves as 
the backup location for the error pages and have a server that will not be 
moved hosting the error page.

I am certain that the DNS protocol allows companies to move web hosting 
servers without killing thousands of customer sites if the hosting company 
does a good job of planning.  I just need help telling them how to do it.

Thanks
George Mizzell