There is no such notion as "XAML script", to best of my knowledge.
To better understand what it is, go to the basics:
http://en.wikipedia.org/wiki/XAML[
^].
Of course you can use XAML to dynamically create some controls or windows, but it does not resemble scripting which is mostly oriented to imperative programming while XAML is pretty much all declarative. If what you had before was already based on scripting system, I'm not sure XAML can fit your needs.
You can implement any type of scripting language on XML, of course.
You can create a data model of your language (even imperative) and develop some engine which would execute the instance of the schema semantically. Any further discussion should involve more or less full specification of your functional requirements (its important to isolate those ultimate requirement from your technological views to avoid preoccupation with the imprinted solutions). Unfortunately it seems to be somewhat beyond the format of our quick Questions-and-Answers.
—SA