RewriteEngine on
RewriteCond %{HTTP_REFERER} ^http:\/\/([^.]+.)*?google.[a-zA-Z_]+ [NC]
RewriteRule (.*) http://www.site-to-redirect-to.com/newpage.html [R=301,L]
RewriteCond %{HTTP_REFERER} ^http:\/\/([^.]+.)*?bing.[a-zA-Z_]+ [NC]
RewriteRule (.*) http://www.site-to-redirect-to.com/newpage.html [R=301,L]