I am using the German version of Word 2013, so I am not absolutely sure, if "quotation source" is the term being used in the English version. I am talking about the automatic text field, one can get via "References" (German: "Verweise"), "Insert quotation" (German: "Zitat einfügen"). Then one gets a drop down menu with all the entries from the biobliography, one can pick one and then an automatic text field is inserted into the text.

After it is hopefully clear what I am talking about, here is the question:

I choosed the citation style "ISO 690" that generates labels of the pattern "(author+year)" in round parentheses. Sometimes I have to append a prefix or postfix to the label, but this prefix/postfix must go into the parantheses. Is there any way how I can do this? For example, I can add page numbers to the end of a quotation label via a special dialog box that appears after a right click onto the text field and choosing "Edit quote" (German: "Zitat bearbeiten").

But there are a lot more cases of optional pre-/postfixes than page numbers. I am looking for a way to add general pre-/postfixes.