Hi Guillermo.You cannot use a custom property as a search field because the search fields are directly translated back to the query that is executed on SQL Server. So, if the column does not exist on SQL Server, the BorwseDialog cannot use the field as a search field.
One way to accomplish this would be to create a view with all the fields you will need as search fileds and use the BrowseDialog on the view. If you decide for this, here is a post to get you started: http://forum.strataframe.net/FindPost20493.aspx