Use a switch by change not on/off status.

[Demon]

Off the top of my head in pseudo-code:

SwitchIn VAR PortB.0
OldState VAR BIT
SwitchState VAR BIT

OldState = SwitchIn
SwitchState = 0

Main:
  IF SwitchIn not = OldState THEN
    SwitchState = SwitchState ^ %1  ' Switch has been toggled
    OldState = SwitchIn
  ENF-IF
GOTO Main

Robert