how to check repeated values in a datagridview cell

Private Sub DGV_CellEndEdit(sender As Object, e As DataGridViewCellEventArgs) Handles DGV.CellEndEdit
Dim iCol = lvwBill.CurrentCell.ColumnIndex
Dim iRow = lvwBill.CurrentCell.RowIndex
Dim cc As Integer = 0
    If iCol = 0 Then
        For x = 0 To lvwBill.Rows.Count - 1
            If DGV.Rows(x).Cells(iCol).Value = DGV.CurrentRow.Cells(iCol).Value Then
                cc += 1
            End If
        Next
        If cc > 1 Then
            MessageBox.Show("Value Already Added in this Gridview")
            DGV.CurrentCell = DGV(iCol, iRow)
            Exit Sub
        End If
' You can make other checking or validations
    End If
End Sub

private void dataGridView1_CellEndEdit(object sender, DataGridViewCellEventArgs e)
       {

           try
           {
               if (e.ColumnIndex == 0) //VALIDATE FIRST COLUMN

                   for (int row = 0; row < dataGridView1.Rows.Count-1; row++)
                   {

                       if (dataGridView1.Rows[row].Cells[0].Value != null &&
                           row != e.RowIndex &&
                           dataGridView1.Rows[row].Cells[0].Value.Equals(dataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Value))
                       {

                           MessageBox.Show("Duplicate");

                       } else
                       {

                           //Add To datagridview

                       }

                   }
           }
           catch (Exception ex)
           {

           }
       }