Nu har jag inte CS3, men detta fungerar i CS2 och CS4:
set L to {}
set D to {}
tell application "Adobe InDesign CS3"
tell active document
set G to file path of item link of all graphics
repeat with I from 1 to count G
if item I of G is not in L then
set end of L to item I of G
else
set end of D to item I of G
end if
end repeat
tell me to set text item delimiters to return
set D to D as string
tell me to set text item delimiters to ""
display dialog "Filer som är monterade mer än en gång:" & return & D
end tell
end tell