I am trying to build two machines which has 1 NRF24L01 modules each, the first one is the transmitter and the other one is the receiver, but when a toggle switch if flicked the roles are changed the transmitter turns to reciever and the reciever turns to transmitter. Is it possible to make it happen or I would have to buy 2 more modules?
What you describe is quite possible
Take a look at
Simple nRF24L01+ 2.4GHz transceiver demo
In particular look at post #4 in that topic