Sorry that I misinterpeted what you were asking in all the years I have been using this program I haven’t had the need to loop anything … I went to the help file …
C:\Program Files\Adobe\Audition 1.5\help\en_US\html\help.html
Basically they want a smooth transition as the wave loops … I pulled this from the help file …
Auto Zero-Cross Edits
Automatically adjusts the beginning and end points of all Cut, Copy, and Paste-type edits to the nearest place where the waveform crosses the center line (zero amplitude point).
If the amplitudes aren’t lined up on both sides of the selection, the endpoints are at different amplitudes. This often results in an audible pop or click at that point.
Smooth Auto-Scrolling During Playback
Enables smooth scrolling when playing back audio in Multitrack View. By default Adobe Audition uses a paging method of scrolling in Multitrack View instead of the smooth scrolling technique used in Edit View. This saves on system resource
I hope it helps, you may want to review the whole section, (which isn’t much by the way) on zero crossing but it sounds like the auto function may be your ticket …. WILLIE