Just in case anyone else ever sees this thread and needs to do something similar then if your page skin has a code behind file then you can use the following code to remove an existing meta tag and replace it with one of your own choosing. I had to take this approach because we have multiple sites on the same installation and only one of those sites wanted their site to be excluded from search indexes. As always use this at your own risk but it works fine on our installation.

Try
'remove the existing MetaRobots entry
page.Header.Controls.Remove(Page.Header.FindControl("MetaRobots"))

'build our own new entry
Dim mymetatag As New System.Web.UI.HtmlControls.HtmlMeta
mymetatag.Name = "robots"
mymetatag.Content = "noindex, nofollow"
page.Header.Controls.Add(mymetatag)
Catch ex As exception
'catch an exception if MetaRobots is not present

End Try

You can use this module to remove the META Robots Tag and then include your own:

http://www.40fingers.net/Weblogsampnews/Weblogs/tabid/58/articleType/ArticleView/articleId/23/First-Beta-release-of-Style-Helper-Skin-Object.aspx