Two ComboBox related in a DataGridView in Visual Studio 2012

I have this code with a DatagridView and two ComboBox, one Province and the Other City, I need that when choosing the province in the first combo, the second combo shows me the cities corresponding to that province

Imports System.Data
Imports System.Data.SqlClient
Imports System.Windows.Forms

Public Class Form1
    Dim CBC2 As New DataGridViewComboBoxCell
    Dim bsProvincia As New BindingSource
    Dim bsProvCiudad As New BindingSource



    Dim CONN As New SqlClient.SqlConnection
    Dim DAprovincia As New SqlDataAdapter
    Dim DAciudad As New SqlDataAdapter
    Dim DS As New DataSet
    Dim DT As New DataTable

    Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
        CONN.ConnectionString = ("Data Source=INFONET\INFOSISTEMAS;Initial Catalog=Localidades;Integrated Security=True")
        CONN.Open()

        Dim DAprovincia = New SqlDataAdapter("SELECT * FROM Provincia", CONN)
        Dim DAciudad = New SqlDataAdapter("SELECT * FROM Ciudad", CONN)

        DAprovincia.Fill(DS, "Provincia")
        DAciudad.Fill(DS, "Ciudad")

        Dim rel As New DataRelation("provincia_ciudad", DS.Tables("Provincia").Columns("id"), DS.Tables("Ciudad").Columns("provincia_id"))
        DS.Relations.Add(rel)
        '--------------------------------------------------------------------------------------------------------------

        Dim bsProvincia As New BindingSource
        bsProvincia.DataSource = DS
        bsProvincia.DataMember = "provincia"

        With mProvincia
            .DataSource = bsProvincia 'DS.Tables(0).DefaultView
            .DisplayMember = "provincia_nombre"
            .ValueMember = "id"
        End With

        Dim bsProvCiudad As New BindingSource
        bsProvCiudad.DataSource = bsProvincia
        bsProvCiudad.DataMember = "provincia_ciudad"

        With mCiudad
            .DataSource = DS.Tables(1).DefaultView
            .DisplayMember = "ciudad_nombre"
            .ValueMember = "provincia_id"
        End With

    End Sub


End Class