A win against Crewe next weekend coupled with a draw or defeat for Bristol City will seal a top two finish.
Calderwood said after the win at Leyton Orient: "It will all be decided next weekend.
"I think the pressure will be on Bristol City because they were almost over the line. They have a week to focus.
"They have a home game and want to win promotion, yet they have no insurance. We have to make sure that if they do not come up to the mark we steal in."
