Hi
If you want to do this on button you could you Mechanical Action defined with button, but if you want to use it to signal in function as you mention you could use signal forwarded by Shift Register to next loop. In this solution you have always your signal and you could change it and you always have it last and actual value.
If you could be more specific with taht what you want to do or if you could show us you VI we could help you little more.
bogdani
