[TYPO3] Show content from another page depending on user group

[Daren Thomas]

Dear list,

The field "Show content from this page instead" in the page headers
works perfectly, if I want to direct all users to the same page. That is
not my situation, however:

I have a page with a bunch of subpages, some of which visible to group
A, some of which visible to group B. The page itself does not have any
content, but is currently forwarded by the "Show content from another
page" feature to the first subpage in the list.

Alas, that page belongs to group A. Users from group B see the empty
page (with dummy header), since they cannot view the specified subpage.

Does anyone have some typoscript or know of an extension that could
handle this situation?

Many thanks,

Daren Thomas