Micro-controller: External Interrupt " RBIE "
Read the port would be the answer.

I found it useful to simply calculate this everytime, as I then get flags for all the states that I might want to deal with, as often it is Pushed or Released I want to know

ThisPort = PORTB   //note you only read the actual port in one place
ThisPort = NOT ThisPort  //if switches pull low
Changed = ThisPort XOR LastPort  //bit set if change of state
Pushed = ThisPort AND Changed    //bit set if change was pushing
Released = NOT ThisPort AND Changed
LastPort = ThisPort