Peter,
This is the section of the knob code that pertains to Knob Mouse Control:
set_control_par($GroupName,$CONTROL_PAR_MOUSE_BEHAVIOUR,1000)
The number at the end, affects the sensitivity of the knob.
If the number at the end (1000) is a positive integer, the knob will have horizontal behaviour.
If you change that number to a negative integer (-1000), the knob will gave vertical behaviour.
