Hi,
No, this is not possible. You can not set a status in such a way it only shows for a specific contact.
However, there is a script that automatically changes your status based on the contacts availability.
http://www.msgpluslive.net/scripts/view/591-Auto-Status+/
Please be aware, that when the status of messenger changes, this new status will show to all contacts.
Regards,
T-PO