[ZPT] adding content to a loaded plone macro

[chris hughes]

Hi all,

I want to add some content to the javascript_head slot in 
main_template.pt, but I have no idea how to add content to a template 
that has already been loaded. I am building a portlet in a custom file 
system skin that needs to add a simple JS function to the HTML head. 
I've tried using a 'fill-slot' metal tag, but I get an error that this 
is only valid in the context of a 'use-macro tag. Obviously, if I 
implement the 'use-macro' tag, I will reload the entire macro and it 
will not be in the proper place. I don't want to modify the standard 
ecmascript files in the Plone skin. Can anybody help with this or offer 
a viable alternative?

Zope 2.7.0, python 2.3.3, Plone 2RC6

Thanks,
chris hughes