Barb. wrote on Aug 23^rd, 2010 at 3:39pm:

But you can also select 'virtual' waypoint manually as you go, as in 'fly this vector for this long'. In order to do this, you need to select your choosen course and the length of the leg on the dopller control panel on the central stand. If you were following the flightplan on the A channel, use the B channel, and then switch. When you do this, the new selected leg will override the flightplan on the world map screen now only showing the new leg you just entered (heading and length) In this case too, the doppler will make automatic corrections and fall back on the active leg if it overshoots it. Switching between channels A and B works just like switching between NAV radios, allowing you to fly to one waypoint while the next one is already set up and ready to be activated.

When I try to switch from the FSX flight plan to one set up on the B channel, it simply resets the values in the windows and the plane goes in circles.  For example, if I'm flying 202 on A with 20 miles to go and set up 180 on B for 20 miles, when I switch the knob from A to B, my B values are reset to 000.  Must you wait until the flight plan gets the next waypoint for it to change to a different route?