Problem with "Fields" in Word?

[dum]

Please, consult me in the following questing.

I'm writing a PhD thesis, using Word's "fields" for correct arrangement of references' numbers, figures' and tables' numbers. For example, if I have first reference to the given book, I'm writing

{SET ref_Book {SEQ ref}}

So, variable "ref" counts the references, when "ref_Book" saves it's value foe the concrete place in the document. Everything is pretty simple, BUT when I'm writing

{ref_Book}

to insert saved number of my reference to the text, I cannot predict, which font will be used by Word to show it. It can be font from "normal" style, it can be bolded or italiced, it size can be more then for other words in the sentence. Unpredictable. I can change the font manually, but after next refresh font will be turned to one, which Word have choosen initially. Tell me please, how it decides, which font should be used and how I can tune it.

Thank you beforehand