Not sure there is such a command Alfa.
This I'm guessing is so you can call the command to save a desktop grab, then you load that up, and set it as the backdrop texture for instance, then restore and maximize the DBPro window, showing the captured desktop. While this DBP app with the captured desktop is running, it could be moving object on the screen, doing 2D effects, whatever really.
There is an old snippet that used an existing DLL to do this, but this seems to be a much more elegant solution, as the DBP app can sit in the background while the screen is captured and loaded, then spring right into life with whatever screensaver it can muster.
One other thing that would help with screensaving is the ability to detect a previous instance, then act upon it. Back when I'd make screensavers in VB4, I would do something like...
IF app.previnstance then quit
So if the app is already running in a previous instance, it quits out maybe switches to that running version as well to avoid abandonment. So if you had a command to return a positive if the current application is already running (or specified application), you could make a much more robust and system friendly screensaver. Without this, you could leave your PC, and come back to 50 versions of your saver trying to run at once... seen it happen a thousand times, it's never pretty!