if iam not mistaken.....azhar wants to interrupt each instruction for debugging purposes...
if that is the case....connect a push button to both, an external interrupt as well as a port pin. when u press it once, the controler will vector to the address location of the external interrupt... in this ISR you can write a code that checks the status of the port pin to which you have connected the push button. the ISR should return to main program when the status at the port pin is changed...
let me know if this works
regards
tushar