Interesting question! I've never thought about this before.
This might depend on the individual and the dialect, so I will only be answering for myself and Australian English.
In a combination is used to describe a series of actions (for example, pressing buttons) being done in a particular order. The actions themselves are the combination.
I pressed the buttons in the right combination.
With a combination is used to describe an action (for example, opening a lock) that needs to use a combination (a particular sequence). The action is not part of the combination.
I opened the lock with the right combination.
So in your question, "in the right combination" is correct.