There never was such a command in AutoCAD, it's always been an add-on Lisp.
http://www.google.com/search?q=add+numbers+in+autocad&rls=com.microsoft:en-us:IE-SearchBox&ie=UTF-8&oe=UTF-8&sourceid=ie7&rlz=1I7HPND_en
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Dean Saadallah
http://LTisACAD.blogspot.com
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