I would just add that what I do in this case is to use a form prior to the report.  I have a combo box on the form which allows the user to select something (the plant in this case).  The Plant ID would go in the combo box.  After the user selects the plant, they click on a button which says something like "Run Report".  The code for that button is the VB code Richard showed, and it references the ID in the combo box.