If Personas isn't behaving the way you expect, always try the same thing in SAPgui. In SAPgui, typing "/o" in the okcode box does indeed pop up that dialog box so that's what I would expect to happen in Personas (2 or 3) also.
If your script then hits the "Generate" button you'll get your new session, or you can include a transaction to open that code in a new session. And if that code is "smen" you can guess what might happen!
So, "/osmen" is what you are looking for...
Steve.