The default material database in SOLIDWORKS is filled mostly with plastics and metals. There is one tutorial in SOLIDWORKS Simulation that is an analysis of a rubber gasket called "Nonlinear Contact Analysis of an O-Ring" which has a rubber material applied to the o-ring. Its material data is shown in the screen shot below. You might want to start by using this. However, you would definitely want to investigate Mooney Rivlin material data for your specific rubber from the material supplier or just generally see if they have a data sheet for their material in Simple Tension that can be input and used with the "Use curve data to compute material constants" option.
In case you need it, here are also instructions for putting material data into a customer material database for use in Simulation (GoEngineer - Simulation: Defining Custom Materials).
Thanks!!! I think my problem is now solved. Thanks again.