[Solved] How to refer to a field on a form

I have a form with a series of list boxes. I want to filter the drop-down content for the list boxes. I know how to filter the drop-down content by setting the Criterion for a certain field. The Problem is that I want to filter the drop-down content according to a value that is not static. The Criterion I want to filter by is a word selected from a separate list box. That way, whenever I change the selection in that separate list box, the filter will change for the list boxes that follow.
Specifically: I have a primary list box that is linked to a table which displays a list of part types. Currently screw, nut, and washer. Then, after the primary list box, there are a series of other list boxes that are linked to a table which displays a variety of descriptions. The descriptions are not specific to one part type. There are descriptions for screws, nuts, and washers all in the same table. The table has a column that refers to part type, and that is what I want to filter by. So, for example, if I filtered by "nut", only descriptions for the nuts appear under the drop-down. The problem is I don't want to filter by a static criteria such as "nut". I want to filter by a criteria that is specified by the primary list box that I mentioned earlier. So what I want to know is how I can describe the field that contains the primary list box so I can enter that as the Criterion for the filter.
Thank you
Specifically: I have a primary list box that is linked to a table which displays a list of part types. Currently screw, nut, and washer. Then, after the primary list box, there are a series of other list boxes that are linked to a table which displays a variety of descriptions. The descriptions are not specific to one part type. There are descriptions for screws, nuts, and washers all in the same table. The table has a column that refers to part type, and that is what I want to filter by. So, for example, if I filtered by "nut", only descriptions for the nuts appear under the drop-down. The problem is I don't want to filter by a static criteria such as "nut". I want to filter by a criteria that is specified by the primary list box that I mentioned earlier. So what I want to know is how I can describe the field that contains the primary list box so I can enter that as the Criterion for the filter.
Thank you