save attachment in a specific name

Goodmorning,
I have created a button with a script that saves the last page and send it as an attachment

var d = this.extractPages(this.pageNum);
d.mailDoc({cTo: "test@gmail.nl", cSubject: "Information" + (this.pageNum+1) + " from " + this.documentFileName, bUI: false});
d.closeDoc(true);

The only thing i can't figure out is how to save the attachment in a specific name.

Does anybody has an idea how i can add this ?

And is it possible to add textfields from within the pdf file to the file name ?

For example mut-Text15 

Thank you very much for youre help !