Thank you all.
I just to prove this probability.
My real problem is that I want to design a vi to simulate a menu(a single level), but if the menu has a multi level, i must call this vi more times.
However, Labview permit only a instance of vi at one time, if I set the vi as a reentrant, it can't show FP and doesn't respose to any EVENT.
Someone say I could duplicate the vi as many as the level of menu,,which may be take more memory.
Anybody has a better solution?