For example if your menu was at http://www.example.com/menu.php then you should be able to put
%%Include.http://www.example.com/menu.php%%
into your template and have it include the menu for you. This will work for any type of file (asp, cfm, php, aspx, html etc) however it would require the server to have the allow_url_fopen option on.
The other option would be if you wanted to just do a php include of the file. In this case you would include it with
%%Include./full/path/to/menu.php%%
which will just do a php include() on the file so it's contents should be parsed as expected. This will also allow you to include plain html files.
For more information on the types of options available for customising your template, see the customising guide at http://www.interspire.com/knowledgemanager/customizationguide.php
