Associa questo codice a "thisworkbook"

codice:
Private Sub Workbook_SheetSelectionChange(ByVal foglio As Object, ByVal Target As Excel.Range)
Static cella As Range
If Not cella Is Nothing Then
    cella.EntireRow.Interior.ColorIndex = xlColorIndexNone
End If
    Target.EntireRow.Interior.ColorIndex = 3
    Set cella = Target
End Sub

'questa parte di codice serve per non ritrovarti l'ultima selezione una volta che chiudi e riapri il file
Private Sub Workbook_BeforeClose(Cancel As Boolean)
    ActiveSheet.Select
    Range("A1").Select
    Selection.EntireRow.Interior.ColorIndex = xlColorIndexNone
End Sub