Load form controls from gridview

Hello I'm new programming and appreciate your valuable help, I have a database with a table called TCOficina, this table is the SqlDataSource of the GridView1. When I open the form the gridview appears filled with all the values ​​from this table. The form is called Oficina.aspx and has this controls: idtxt.Text, codtxt.Text, oficinatxt.Text, CheckBox1, fechatxt.Text and usuariotxt.Text. Clicking SELECT gridviwew brings me all the values ​​of the row select and load the respective controls, except the checkbox, how do I load the value GridView1 checkbox on the form, thank you.

Protected Sub GridView1_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles GridView1.SelectedIndexChanged



        idtxt.Text = GridView1.Rows(GridView1.SelectedIndex).Cells(1).Text

        codtxt.Text = GridView1.Rows(GridView1.SelectedIndex).Cells(2).Text

        oficinatxt.Text = GridView1.Rows(GridView1.SelectedIndex).Cells(3).Text

        'CheckBox1.Text = GridView1.Rows(GridView1.SelectedIndex).Cells(4).Text     **********no se**********

        fechatxt.Text = GridView1.Rows(GridView1.SelectedIndex).Cells(5).Text

        usuariotxt.Text = GridView1.Rows(GridView1.SelectedIndex).Cells(6).Text

        lblCuenta.Visible = False
        Me.btnGuardar.Visible = False
        Me.btnActualizar.Visible = True
        Me.Button2.Visible = True

    End Sub