Can the same member be part of more than one subcategory?
You can add a text field and format it with a value list of sub categories. You can use radio buttons if they are only to be part of one subcategory. If several selections may be possible you can use check boxes.
Use manage | Value lists... to create a value list--you can just type in these values here using the custom values option.
You can then define a text field in your table and add it to your layout.
On the layout while in layout mode, select this new field and use Field /control | Setup... to change it from an edit box to either radio buttons or check boxes. (You could also use a drop down list or pop up menu if you prefer.) You'll find a drop down list of value list to select from to specify your new value list in the field/control | Setup dialog box.
It worked! Thank you so much for your help.
Have a great weekend!
All my very best