You don't mention what you are opening on your switch board when you click on Category? Is a form opening with a list box are you using a combo box? I'm sure your not trying to type a number in from memory?
Here is what I would try. Create an unbound form with a list box and populate it with the data you want to pull records up for. This can be accomplised by handling the data to be filled on the on Open event of the form by doing some SQL
Private Sub Form_Load()
With me.Category 'the name of the list box
.RowSource = _
"SELECT DISTINCT Category FROM MyMainTable " & _
"WHERE Category IS NOT NULL"
.LimitToList = true 'if using a combo box
End With
End Sub
Now you have your criteria. So now you need to display it. On the top of the form you just created add the following
Dim strFilter as string
Now on the double-click event, or after update event or for that fact whatever event you want to fire this code on of the list box add the following code.
strFilter = Me("Category"

DoCmd.OpenForm "frmIwanttodisplayhere", , , "nameof tableholdingmydatahere= " & strFilter
Good luck. Life's a journey enjoy the ride...
jazzz