Ciao Steve,
the selection property of iTunes returns a list of selected tracks.
Once you have created this list you loop through the contained tracks and do something with these tracks, for example
tell application "iTunes"
set s to selection
repeat with aTrack in s
set n to name of aTrack
display dialog n
end repeat
end tell
this is difficult, because the next song in the list you see is not unconditionally the next song
in the library of iTunes. I would write a script processing a selection of tracks,
which is more reliable.
Take a look at Doug Adams’ huge collection of AppleScripts,
maybe you dont’t have to reinvent the wheel