Search the plug-in reference for "AutoPan." On your audio channel, under inserts, it is under the "Modulation" sub category.
Another way to do what you are wanting is with Automation of the pan in the channel.
Easiest way to do that is to enable the "Automation Write" in the channel (or globally), then while the song is playing, move the pan as you desire. Automation will "record" your actions. Look in the Operations Manual, p. 280, "Writing automation data" for details.
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