ADir() seems to work ok when changing diskettes:

dimension aFx3[01,05]
?adir( afx3, "*.*" ) && just checking syntax of ADir()
display memory like afx3

?adir( afx3, "a:\*.*" )
display memory like afx3 && only 1 file on this one
clear && swapped diskettes here...

?adir( afx3, "a:\*.*" )
display memory like afx3 && 2 files on this one

Is this what you are seeing?