Either party can file a modification to increase or decrease support based on a change in circumstances. If the CP makes more money and the NCP finds out, the NCP can file for a downward modification. If the NCP makes more money and the CP finds out, the CP can file for an upward modification. If either party loses a job or is laid off, either party can file for a modification.
However, some states limit how long of time can pass between modifications. In some states it's one year, some two, some three. I don't know OK laws, but there is a link on this board to the laws of all states.
"I owe nothing to my brothers, nor do I gather debts from them. I ask none to live for me, nor do I live for any others. I am not the means to any end others may wish to accomplish. I am not a tool for their use. I am not a sacrifice on their altars." Ayn Rand