What FE program are you using? The Mooney-Rivlin model can be calibrated by, for example, both Abaqus and ANSYS.
Also, what material are you interested in? I rarely use or recommend the Mooney-Rivlin (MR) model. There are other material models that are equally accurate, easier to calibrate, and more robust.
I might be a bit biased on this, but the MCalibration application is absolutely fabulous for material model calibrations. If you haven't you should check it out.
Jorgen Bergstrom, Ph.D.