When I publish my ASP.NET MVC application it generates a app_offline.htm file to take the site offline while it updates the website and then deletes the file once the publis
You can use a batch file which calls the compiler with the current directory information as parameters... It then copies app_offline.htm and copies the new file over. Run it from where the source is.
I personally use a program which is just a bit more elaborate then the batch and also checks hash's of files to determine if they need updating makes a zip of new files and extracts it to the remote host and eliminates files we designate are for unit testing when going from test to production. I have also combined SVN integration into my solution so when you publish for test or production you also optionally commit to SVN. The program is stored on a network drive and is called from a batch file on the local PC with the current directory info. This way dev's dont have to update to the new deployer or the app_offline if any changes occur. Finally it removes the app_offline.
Check out http://msdn.microsoft.com/en-us/library/system.web.compilation(v=vs.80).aspx for more info or http://msdn.microsoft.com/en-us/library/ms229863(v=vs.80).aspx if you are just making a quick batch!
Additionally in the post you initially referenced and I have also verified you can actually change it but you change it for others using the publish feature as well. This is why you were given the answer you were.