create name lists i.e. MainCategory: Plumbing, Electrical...
Sub Categories: Switches, Recepticles...

Then you can create cascading Combo Boxes on your user form.
Set up the initial Combo Box (MainCategoery) to load when the USer Form Opens,
Then the next (SubCategory) to Load when the first Cbo changes:
Private Sub CboMainCategory_Change()
Me.CboSubCategoery.RowSource = CboMainCategory.Value
End Sub