Holiday absence tracker, holidays, or present won't change when selecting new dates

I think that need to use VBA in worksheet "HOLS ABSENCE".

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
    Dim Rng As Range, rINT As Range

    Set Rng = Union(Range("I4"), Range("K4"))
    Set rINT = Intersect(Rng, Target)
    If rINT Is Nothing Then Exit Sub
    Range("N8:AZ1000").ClearContents
End Sub