Let's say there is an organization that has a Pushkah (charity box) that I regularly insert money into for Tzedakah purposes, then this same organization has a Chinese auction and I want to get a chance at a particularly pricey prize. Can I use the money in the Pushkah for the Chinese auction? Same organization, new motivation. (Of course CYLOR.)
Presumably the money in the tzedahkah box is for tzedakah.
Money spent at a chinese auction, does not count as Tzedekah since you are receiving the possibility of gaining an item for the money spent.
However, if you plan to give any item you win the auction to Charity as well, then I presume you could use the money from the Tzedakah box to do so. If such an idea seems crazy to you, then I think you have a better understanding of whether or not this is being done for tzedakah or your own possible personal gain.
The above quote, found here, gives a formula by which one may use maaser / tzedakah money for a Chinese Auction (a.k.a. raffle).
The question also asks whether previously set aside money for an organization can be used to purchase a ticket for a raffle run by that same organization.
Using the stipulation quoted above, it would seem that handing over the money to the organization by means of a losing raffle ticket is no different than giving it to them directly.
Since you have stipulated that any winning raffle ticket is retroactively considered to have been purchased from your own money - if you win, you would then "owe" the original price of the raffle ticket (NOT the value of the prize!) to the organization.
Now - what if one had already placed money into a pushka (charity box) with intent to give that money to a specific organization? Can that money be used to buy raffle tickets from the same organization?
If the pushka is in your own home, the money still belongs to you. You have merely designated your own money to give to organization X.
If you empty the pushka to buy Chinese auction tickets from organization X, they have still received the money. Putting money in a box at home is NOT like "hekdesh" (consecrating an object for Temple use). For example, if you suddenly needed change for the parking meters, you could take the money back. (It is unclear whether or not you would then "owe" an equal amount of money to that organization.)
This is all true because of the concept of tova'as hanaa. Tova'as hanaa is the power of choice that a charity giver has when distributing his charity funds.
This power of choice is considered valuable enough to marry a woman with it (in lieu of a ring)
So, just because you put your own money in your own box, with organization X in mind, that doesn't remove your tova'as hanaa on the money. Certainly if you could legally use the money for a completely separate purpose, you could use it to buy charity raffle tickets.