You can, to do it you need a target waypoint, if you don't have on already that you have available to move you can convert a waypoint to a target waypoint by selecting "Takt" on the computer mode selector, then select "In" and enter 9, after entering 9 press the button for the waypoint you want to convert. After doing that, you select the waypoint by going into computer mode "Akt Pos" and pressing the waypoint button. When you have selected the target waypoint you can make a fix on the target location.
Edit: As stated above make sure you don't make the fix when you have a regular (B) waypoint selected as this will screw up the entire flight plan. :-)
Correct, but i would start by making it a target point (M=Mål=Target) BEFORE making the fix, to avoid screwing up the flight plan. :-)