Dim lista As New Dictionary(Of DataGridViewCell, String)
    Dim valoreTemp As String

    Private Sub DataGridView1_CellBeginEdit(ByVal sender As DataGridView, ByVal e As System.Windows.Forms.DataGridViewCellCancelEventArgs) Handles DataGridView1.CellBeginEdit
        valoreTemp = sender.CurrentCell.Value.ToString
    End Sub

    Private Sub DataGridView1_CellEndEdit(ByVal sender As DataGridView, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellEndEdit
        If (valoreTemp = sender.CurrentCell.Value.ToString) = False Then
            If lista.Keys.Contains(sender.CurrentCell) = False Then
                lista.Add(sender.CurrentCell, valoreTemp)
            End If
        End If
    End Sub

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        For Each cella As DataGridViewCell In lista.Keys
            If (cella.Value.ToString = lista(cella)) = False Then
                cella.Style.BackColor = Color.Yellow
            Else
                cella.Style.BackColor = Color.White
            End If
        Next
    End Sub