tried with code as you suggested but it doesn't work either. As soon as I make a changes on the dropdown boxes on sheet "Case Files" it hides all 3 rows in "Magistrates" sheet and does not unhide them again.

Option Explicit

Private Sub Worksheet_Calculate()
Dim i As Long
Application.EnableEvents = False
For i = 18 To 20
Rows(i).Hidden = (Len(Trim(Cells(i, 2).Value)) = 0)
Next
Application.EnableEvents = True
End Sub