Bueno un avance ya no me da error...
http://www.wineup.cl/wineup/ejemplo6.aspx
el detalle es que no me esta mostrando los datos en el segundo listbox...
Este es el codigo:
Private Sub MySelect_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs)
'Handles MySelect.SelectedIndexChanged
'Aqui ejecutas la consulta
'Dim varieda as string
'Varieda= MySelect.SelectedValue.ToString()
MyConnection2 =New OleDbConnection("PROVIDER=MICROSOFT.JET.OLEDB.4.0; DATA SOURCE=" & Server.MapPath("../yyyy/mmmm.mdb"))
Dim DS1 As DataSet
Dim MyCommand1 As OleDbDataAdapter
MyCommand1 = New OleDbDataAdapter("select * from vinos where Variedad=MySelect.SelectedValue.ToString()", MyConnection2)
DS1 = new DataSet()
MyCommand1.Fill(DS1, "vinos")
MyList1.DataTextField= "cepa"
MyList1.DataValueField ="cepa"
MyList1.DataSource= DS1.Tables("vinos").DefaultView
MyList1.DataBind()
End sub