email link to network site owners

Hi
I am using marketpress, and a copy of gridmarket on my multisite install. What I'm trying to do is add a link to a certain page on seller's sites so that a potential buyer can click on it, and be brought to a contact form that will be sent to the seller of that particular site.

I typically use contact form 7 on my sites, but it doesn't appear to be working. Is their a wpmu or other plugin that will help me with this?

Any advice would be appreciated

Thanks
Andy