All responses have helped to some degree, Greg suggested that I did not need to acknowledge that the event had been handled, this would be true under normal circumstances. But, events are being triggered fom a state machine in my main C++ app, these events would normally be handled by another app in c++. However I am developing a system which will allow LabView developers to hook into our app with their own custom code and as such acknowledgement is essential to ensure that the state machine is made aware of the current status of the user code. I could use a sub vi as you suggested which would remove my problems - but I was looking at creating a generic vi which developers could use - clearly a sub vi could only contain 'generic code' and not code specific to user requirements. As a first example I could provide users with a sub vi approach - but only as an example as how they could develop their own system. I am currently looking into geeting the callback vi to generate a user event to signify that the event had been handled which could be picked up by the main vi ...
I hope this make sense to you ? regards Stephen
