on the results page, go to the bindings panel, click the plus button and select "URL Variable" name it "S_gallery_name"
on the server behaviors panel, click the plus button and select Data Assist -> dataAssist Search
for the trigger, click the lightning bolt and select the S_gallery_name URL Variable.
next add a new criteria, select the gallery name column.
For Filter type select List.
For List Field Name, click the lightning bot icon and select the S_gallery_name URL variable.