I don't see an option for what we do....
We have a monthly tournament, T1500, with one re-buy in the first three rounds. IF someone re-buys, then I allow add-ons, if and only if, you are under 1500 chips, and if you can buy chips in multiples of $5 dollar increments and not go over 1500 in chips. This way, if someone re-buys (usually twice a tournament), then we allow everyone the option of adding on right then and there, if they qualify for chips at all.
For example, if we play for $25 buy-in and re-buy, your add-on of $5 gets you 300 in chips. You can add-on as many chips in increments of 300, as long as you don't excede 1500. This is set so that you can't buy more chips than a player who has re-bought, and so that you are at a disadvantage to a player who has re-bought.
Aluvial