Now you have a way to fire the Value change event, but the problem is it is in another value change event. You've got a catch-22. The only way the event will ever run is if you execute the value change (signalling) property node. But the property node is in the event that will never run.
And worse, if the event would ever run because you had a value change property node execute somewhere else, that event would keep queueing up further events because of the property node in it. You'd essentially create an endless loop of events.
I don't know about your 0-20 requirement, since you've only added a zero constant to that.
I'd suggest you read some tutorials if you haven't done so already.
LabVIEW Introduction Course - Three Hours
LabVIEW Introduction Course - Six Hours
Look at examples on how the event structure works and read up on it in the help file.
Turn on execution highlighting so you can see how your program is or isn't executing.
For all of that, the event structure may not be the best way for you to do the screen captures. Event structures are primarily designed to handle user interface events, but can also handle programmatic events such as value (signalling) property node and user events. But it is generally a bad idea to have multiple event structures, especially ones that are handling the same events as you are doing now. It can be done, and there is nothing inherently wrong with it. But if you don't understand the architecture of your program, you might lead yourself down a path where the program no longer behaves like you expected it to. You might be better off using a queue or notifier to trigger your separate loop to capture the screenshots.
