Someone who doesn’t have any money to buy neros Erev Shabbos Channukah, however he has a coat he could sell. When he sells it and is able to buy a ner should he use it for Shabbos or Channukah (since the halacha is that neros for Shabbos comes first, however the person wasn’t machuyiv to sell his coat for neros Shabbos.)
This is a famous question, which has been asked by the Rav of Ponavitz and others.
It stands to reason that if one sells one’s coat for Chanukah candles, one does not have to spend the money for Shabbos candles. The obligation to spend the money for Shabbos candles will mean that there is no obligation to sell the coat. Therefore, it is considered as though the money is specifically reserved for Chanukah.
I have not looked up sources, because I don’t image this question was asked because of practical considerations. I leave finding the sources to the learned questioner!