Hiding Rows with VBA based on a dropdown List

Knimmo 

Right-click the sheet tab.
Select 'View Code' from the context menu.
Copy the code listed below into the code window.
Close the Visual Basic Editor.
Save the workbook as a macro-enabled workbook (*.xlsm).
Make sure that you allow macros when you open it.
Code:

Private Sub Worksheet_Change(ByVal Target As Range)
    Dim n As Long
    Dim m As Long
    If Not Intersect(Range("C4"), Target) Is Nothing Then
        Application.ScreenUpdating = False
        Application.EnableEvents = False
        m = Range("B:B").Find(What:="*", SearchOrder:=xlByRows, SearchDirection:=xlPrevious).Row
        n = Val(Range("C4").Value)
        Range("A7:A" & m).EntireRow.Hidden = False
        If n >= 0 And n < m - 7 Then
            Range("A" & n + 7 & ":A" & m).EntireRow.Hidden = True
        End If
        Application.EnableEvents = True
        Application.ScreenUpdating = True
    End If
End Sub