Problem with Intersect(Target)

Hi,
I need to controll if into a range of cell the max item will be two.
If the user write the vlue and play enter, or right arrows the function ready, if the user play the mouse into another cell or use a left, up, down arrows the controll don't go.
any ideas???

thank
Fabrizio

Private Sub Worksheet_Change(ByVal Target As Range)
If Intersect(Target, Range("D12:T385")) Is Nothing Then
    Exit Sub
    Else
    Dim stDocName1 As Variant
    Dim stDocName2 As Variant
    Dim stDocName3 As String
    stDocName1 = ActiveCell.Row
    stDocName2 = ActiveCell.Column
    stDocName3 = "Sorry" & vbCrLf & "two operator will be in Holiday into some day"
    Select Case stDocName2
        Case 4 To 9
            Range(Cells(stDocName1, 4), Cells(stDocName1, 9)).Select
            If WorksheetFunction.Count(Selection) > 2 Then
            MsgBox stDocName3, vbExclamation, "Holidays Planning"
            Cells(stDocName1, stDocName2).Value = Null
            Cells(stDocName1, stDocName2).Select
            End If
        Case 10 To 14
            Range(Cells(stDocName1, 10), Cells(stDocName1, 14)).Select
            If WorksheetFunction.Count(Selection) > 2 Then
            MsgBox stDocName3, vbExclamation, "Holidays Planning"
            Cells(stDocName1, stDocName2).Value = Null
            Cells(stDocName1, stDocName2).Select
            End If
        Case 15 To 20
            Range(Cells(stDocName1, 15), Cells(stDocName1, 20)).Select
            If WorksheetFunction.Count(Selection) > 2 Then
            MsgBox stDocName3, vbExclamation, "Holidays Planning"
            Cells(stDocName1, stDocName2).Value = Null
            Cells(stDocName1, stDocName2).Select
            End If
    End Select

End If
Application.EnableEvents = True
End Sub