it's based on URL

So does that mean that if a user is browsing to
my1st_url.com/index.php he will see vba page 1
while when browsing
my2nd_url.com/index.php he will see vba page 2?
because both locations are are the same file.

that is correct :up:

awesome mod!
/clicks install and nominate for MotM

Does this address the problem of the vBA 'home' link on the mobile portal still pointing back to the main sites domain?

a true genius. thank you for this mod!

You would need to somehow do a temp change to bburl and homeurl.
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My setup is slightly different. I have my forums on myforums.com -- but I want to set up vBa CMPS "front pages" on mydomain.com. It works just fine (after cleaning up the style, so that links are properly set up) except for the "Welcome Block", which does not update the myforums.com login status while looking at mydomain.com. Is there a way to fix this?

Update: I'm tinkering around with this add-on, and it looks like it works well, but I only want it to display/force a specific "frontpage" depending upon the domain (i.e., if no specific page has been designated). How can your plugin be modified to allow this to function properly?

I don't really understand what extra functionality you're asking for - what you're describing sounds like what this already does. What do you mean by "Frontpage"?