Is there some file I can to dreamweaver that would support unityscript highlighting and autocomplete?
I seriously doubt you could do that.
What is your reasoning for this? If you are looking for a decent script editor download Visual C# express and set it as your default text editor.
It supports all the Autocomplete and syntax highlighting you would require.
As far as I know, Dreamweaver does not have such a function, but you can find an alternative and another program that uses it. As far as I know, BlueGriffon uses something like this. You can read about it in this article best Dreamweaver alternatives - 10 Free Dreamweaver Alternatives for Windows and Mac - TechMused
I hope to be useful