Excuse me Henrik, If you read the spec. sheet you can set the interrupt edge for the INT0 and INT1. It is not required to set it each time. Also the interrupt routine look like:
'************************************************* ********************
INC_C: 'INTERRUPT SERVICE ROUTINE FOR EXTERNAL INTERRUPT-0
'************************************************* ********************
POSITION = POSITION + 1
@ INT_RETURN

'************************************************* ********************
DEC_C: 'INTERRUPT SERVICE ROUTINE FOR EXTERNAL INTERRUPT-1
'************************************************* ********************
POSITION = POSITION - 1
@ INT_RETURN

That's all there is to it.