There should be, based on what I've seen with DOS (command) windows.
If you have one, the title bar text is the normal title bar text. If you then open a second one, the first gets a  appended to its title bar text, while the second gets a . You can refer to them by that title bar text with the included square brackets and number.
I have seen this relating to command windows, but haven't tried with a normal Windows app. If it doesn't work, there may be other ways I'm not aware of...
While we're on this topic, I've been working on something similar. We would like to be able to test 2 versions of our software. The frame is shared between the versions because the interface is quite similar.
Our application is declared as a winclass that we make instances of. I've been able to Invoke both versions by passing the command line into the instance and having a dynamic window tag (so SilkTest can distinguish between them by the tag). The problem with this is that you cannot use the "Record Window Identifier" dialog, since the tag in the frame is a variable.
If I use a static string for the tag I can invoke both versions but I cannot distinguish between the two instances of the application. I can use the "Record Window Identifier" dialog though.
I was wondering if anyone else has done anything similar and what they came up with. I think I'm close but I'm running out of ideas. I'm beginning to think its not possible. Any ideas would be great. Thanks,