MScrm 2011 : filtered lookup for Add existing button on the form ribbon:





http://www.magnetismsolutions.com/blog/paulnieuwelaar/2013/02/04/filter-n-n-add-existing-lookup-dynamics-crm-2011-rollup-12


http://danielcai.blogspot.in/2011/12/filtered-lookup-for-existing-button-of.html

http://community.dynamics.com/crm/b/magnetismsolutionscrmblog/archive/2013/02/04/filter-n-n-add-existing-lookup-dynamics-crm-2011-rollup-12.aspx#.UXaQ-krAQdM

http://www.mscrmking.com/2011/06/crm-2011-how-to-filter-add-existing/

http://blogs.huddle.com.ar/sites/Dynamics/Lists/Posts/Post.aspx?ID=14