Ho risolto così:
Public Shared Function OpenInNewPage(ByVal Page As Page, ByVal Address As String, Optional ByVal SimpleWindow As Boolean = True) As Boolean
Dim ClientScriptName As String = "Nome"
Dim ClientScriptType As Type = Page.GetType
Dim Cs As ClientScriptManager = Page.ClientScript
If Not Cs.IsStartupScriptRegistered(ClientScriptType, ClientScriptName) Then
Dim ClientScript As String = "<script type=text/javascript>window.open('" & Address & "','_blank', 'channelmode=no,directories=no,navigationbar=no,location=no,locationbar=no,menubar=no,resizable=yes,scrollbars=no,status=no,titlebar=no,toolbar=no,width=950,height=880');</script>"
Cs.RegisterStartupScript(ClientScriptType, ClientScriptName, ClientScript, False)
End If
End Function
Prima setto la variabile di sessione e poi utilizzo la funzione creata che mi inserisce il codice java.
ciao.