custom annoucement by referrer url??

[Jolten]

I'm not sure where this should go so I posted it here. My apologies if it's in the wrong place.

I know how to set up custom announcements based on users/usergroups/page/etc. What I'm wondering is, is it possible to set up a custom announcement based entirely on the referring url? If my site gets a grea tmany hits from ... oh... say... www.thissite.com, is it possible to set up an announcement which basically looks like:

<if condition="referring url == www.thissite.com">
Stuff
</if>

Thanks

[Jolten]

anyone?