Hey 2009luca, this is how I do it. There may be better ways, but this is how I know to do it. Here is the full code, you may not need it all, but I don't want to leave anything out.
' Get the necessary Session Object
Dim Sess0 As Object
SessName0$ = "MYSESS0_2.edp"
Set Sess0 = Sessions.Item(SessName0$)
If Sess0 is Nothing Then
Err = MsgBox(SessName0 + " is not currently open. Open it?",1)
If 1 = Err Then
Err = 0
Set Sess0 = Sessions.Open(SessName0)
If Err Then
MsgBox("Failed to open " + SessName0 + ". Stopping playback")
Stop
End If
ElseIf 2 = Err Then
Stop
Else
MsgBox("Failed to open " + SessName0 + ". Stopping playback")
Stop
End If
End If
If Not Sess0.Visible Then Sess0.Visible = TRUE
Sess0.Screen.WaitHostQuiet(g_HostSettleTime)