How do I pass UDF Variables between StackScripts?

I've been looking everywhere and I can't seem to find any way to do this. I am calling other stackscripts like so

<ssinclude StackScriptID="1">

and I am hoping you can do something like

<ssinclude StackScriptID="1" username="user" password ="..." ...etc>

Let me know if it's possible or not, thanks.