combine scripts in asp.net ajax toolkit

We are using version 3.0.20229.0 of the asp.net ajaxControlTookKit (before .net 3.5 sp1). I was wondering if I can combine our custom javascript files into the ScriptResource.axd that the controlTookKit creates. I’ve found this article (http://blogs.msdn.com/delay/archive/2007/06/11/script-combining-made-easy-overview-of-the-ajax-control-toolkit-s-toolkitscriptmanager.aspx)
which tells me that I need to add the scriptCombine attribute to the assembly file. We are running a WebSite project, how can I add this attribute?