I guess the information you have provided here isn't sufficient and clear! Anyway what I understand is an aspx page is already working based on XML input. You want to know whether that can be made to work with Sql server? If my understanding is right .. read on:
You can almost use the existing code (though i can tell it for sure only after having a look at the code). Just connect to the DB and fetch it in a DataSet. From a DataSet you can create a XML file. The rest of the code will work automatically as it was coded to work for a XML input
Best Regards
Vadivel
MVP ASP/ASP.NET
http://vadivel.thinkingms.com