Allow access to a blocked site based on site that links/embeds it

[James Robertson <j@xxxxxxxxxxxxxxxx>]

We have an acl that blocks certain websites, specifically youtube.

A website used by staff for work has started publishing training
videos on youtube and embeds them in their webpages and we need to
allow access to these without allowing access to all of youtube.

Is it possible to somehow allow these particular videos from youtube,
perhaps based on the site that is linking to them?  Or by some other
method?

Thanks