Can you explain how you've designed your objects?
As I see it, ideally you'd have 3 components: a process, an object for the 1st web app, and an object for the 2nd web app. Of course you may need more than just one object for each web app, but I'm going with simplicity.
You would need to create actions in each of the objects that handles launching, attaching, reading, writing, etc.
I'm not sure, but the error you're getting makes me think you're trying to work with two web apps from within the same object. This is possible, but it will be a nightmare. It's best to have separate objects.
So, let us know what your set up is for those components, which should help shed some light.
Dave Morris, 3Ci at Southern Company