I USED "CALL BY REFERENCE NODE VI" TO CALL SEVERAL SUbROUTINS WHICH FINISH DIFFERENT TASKS. But it's very strange. I mimic the dynamic loading example in labview. only the "stop "button always stops the program. other buttons don't always respond to my request. some times it runs(calling the subroutine), some times just no response, some times give out error"1031 occured at open vi reference in IMPULSE RESPONSE VI. Possible reasons: vi reference type does not match vi connector pane.