VB .NET & ASP on a columnbutton

Hi all, i am doing a new asp project using visual studio .net (VB.NET), what i have done by this code, i have binded the datagrid to a datareader and then added a columnbutton, this code works very fine but . it seems i cant trap the click event on the button in the column

Can anyone advise me in details how can i track the click button and identify which item in the grid is clicked to open the alternative page.

HERE IS MY CODE

VB Code:

If IsPostBack = False Then
            Dim db As New OleDb.OleDbConnection(dbstring), cmd As New OleDb.OleDbCommand(Session("sql"), db), readx As OleDb.OleDbDataReader
            Dim colx As New ButtonColumn()
            colx.CommandName = "viewcmd"
            colx.ButtonType = ButtonColumnType.PushButton
            colx.Text = "View"
            db.Open()
            readx = cmd.ExecuteReader
            dbgrid1.DataSource = readx
            dbgrid1.Columns.Add(colx)
            dbgrid1.DataBind()
            readx.Close()
            db.Close()
            Exit Sub
        End If

THX in Advance