Ah the old staple filter sweep.
You can also use the autofilter, but put the Threshold at the maximum, so that the envelope doesn't trigger. You actually have less control over the sound but you might prefer this for a filter sweep function.
Open the automation lanes in the arrange window by pressing A. Next you need to set the automation lane to control the filter cutoff. Select it in the box that indicates what the lane is controlling (should by default say "Volume"). Filter cutoff should be in Autofilter -> Cutoff. You can then click in the nodes in the arrange window over your audio region to create a filter sweep (either up or down).
btw i might also add that the best filter i've ever used for sweeps is the Sonalksis TBK filter. They have a 30 day demo where you can try it (i did that, but i bought it after about 3 days). The sound quality is in my opinion the best you can get for a plugin.