HMC835 Manual calibration

I have an HMC835 working quite well in my system.  I want to speed up the tuning by using manual calibration.  I am able to successfully read back any/all registers but after tuning to a new frequency (integer mode) when I read back register 0x15 I always get the factory default instead of the currently tuned frequency data.

Is there some other register setting that causes the auto-calibrated data to appear in register 0x15, or is there some special sequence that causes this

thanks

Fred