Yes,
The normal track Faders are always located Post track inserts. By using the volume plugin, this will allow you to put a fader pre or post another FX. It acts just like any other plugin, where you can arrange the order of the FX processing. Therefore within the track insert chain, you could put a Volume fader prior to the gate and eccentially control the input feeding the gate. The Volume fader is an automatible effect and you can therefore automate this level adjustment.

Also, the Sony Track Gate is automatible. So you could also use that as an automated gate and adjust the Threshold level.