Don C. TROSSMAN, Plaintiff and Counterdefendant-Appellee, v. Thomas D. PHILIPSBORN, Andrew I. Philipsborn, Daniel C. Bartok and John J. Lynch, Defendants and Counterplaintiffs-Appellants (Oak Park Partners, Ltd., and Burnham Investors, Ltd., The Philipsborn Company, Philipsborn Development Corp., and Clarion Development Limited Partnership, Defendants).