Cubase5 - "Edit Active Part Only" question

hi all

i am looking for a way to make all inactive-track’s notes totally unselectable

lets say there are 2 tracks, named A,B
when i do multi-track editing in Key Editor,
“Edit Active Part Only” is ON
and A is the active part

i can still select/drag B track’s notes just by clicking them, and then B track becomes the active part !!!
( “Edit Active Part Only” only restricts ‘select all’/ select notes by clicking and forming a rectangular box )

it drives me crazy, any suggestions ? :unamused: