Now I see... I have never used it and Input (Gain/Pan) section is normally outside of my screen (I still use low resolution 3/4 display). I have never tried scroll the Inspector for buses
Unfortunately, I have not found any spells of this parameter in Sonar Control Surface API. It still can happened it is available throw some undocumented parameter combination, these are hard to find till some source code from CW make use of it (and in case of Input Pan, it looks like Cakewalk has never used it, even on VS-700). So I will try to dig for it (once some idea comes in my mind where to look).
Thanks for the information!
EDIT. I try to ask on forum first... With a hope CW knows the answer.