In Reibman v. Senie (302 AD2d 290 [1st Dept 2003]), the Appellate Division, First Department, noted that: In order to establish proximate cause, plaintiff must demonstrate that but for the attorney's negligence, plaintiff would have prevailed in the matter in question or would not have sustained any ascertainable damages. Stated another way, plaintiff is required to prove a "'case within a case.'" The failure to establish proximate cause mandates the dismissal of a legal malpractice action, regardless of the negligence of the attorney [internal citations omitted]. 302 AD2d at 290-291.