Auto generation of workcells using shape file and USNG

[Bauerr]

While observing R3 create workcells for tornado response in OK they had one request to add a feature. When the shapefile for the county was imported and the USNG grid was used to create workcells it appears the upper left and bottom right X.Y of the shapefile was used to create the workcells This created a box with many extra workcells that were outside the county and had to be deleted manually. Is there a way to create workcells in this manner that only includes workcells within and intersecting the shapefile?