Datagrid and ADO recordset

I want to fill a datagrid using a ADO Recordset I have opened
previosly, but it doesn't work. Thhat's my code:
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Option Explicit
Public cnnoddo2 As ADODB.Connection
Public rstactivos As ADODB.Recordset

Private Sub Cmdrellenar_Click()
Dim Sql_activo As String
Set rstactivos = New ADODB.Recordset
Sql_activo = "SELECT activo FROM activo_subyacente"
rstactivos.Open Sql_activo, cnnoddo2, adOpenDynamic,
adLockOptimistic
Set DataGrid1.DataSource = rstactivos
End Sub

Private Sub Form_Load()
Dim strconexion As String
Set cnnoddo2 = New ADODB.Connection
strconexion
= "ODBC;DATABASE=ODDO;DSN=odbcoddo2;UID=sa" 'cadena de conexión
cnnoddo2.Open strconexion
End Sub
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Can anybody help me?. Any advice will be greatly apreciatted.
Nauj