I am trying to create an AF element attribute that calculates the flow to a specific vessel. The flow meter is shared, so I need to first determine if the vessel's valve is open. I have already created that attribute 'Valve' in AF, and it currently has a digital state of "Closed". If V=Valve and F=Flow, it seems that I should just be able to do V*F and have my answer. But AF doesn't seem to like that and reports "Data was not available for attribute 'Valve', even though it clearly has data. I also tried an if-then-else statement, with the same results. AF won't let me do a string comparison, and doesn't seem to have any functions to look up the digital state value (which would be 1 or 0). Am I out of luck in AF? I am really starting to like AF except for this hitch.