OmniFocus: Schedule Followup (applescript)

Thanks to Tim @ Omni for pushing out a quick fix to allow this script to be. I've already used it half a dozen times:

-- schedule a followup of the selected items 7 days from now... more to come

tell application "OmniFocus"
  tell first document window of front document
    set thetrees to selected trees of content
    repeat with idx from 1 to count of thetrees
      set atask to value of item idx of thetrees

      set newtask to duplicate atask to after atask

      set due date of newtask to (due date of newtask) + (86400 * 7)
      set name of newtask to "Followup: " & name of newtask
    end repeat
  end tell
end tell