Why not try something straight forward as this?

Code:
     ' run this every second along with your clock code
     if (Hours >= Set_Hours AND Minutes >= Set_Min AND Seconds >= Set_Sec)
           OT_Seconds = OT_Seconds+1
           if (OT_Seconds > 59)
               OT_Seconds = 0
               OT_Minutes = OT_Minutes+1
               if (OT_Minutes > 59)
                    OT_Minutes = 0
                    OT_Hours = OT_Hours+1
                    ' you may want to restrict / rollover the hours to 24 hours format here.
               endif
           endif
     endif