So I've managed to get screenshot saving with my app working using this bit of code:

ExternalStorageDirectory$( "Android object" ) + "/DCIM/Camera/" + "Screenshot.jpg"

Not sure if that's all correct but it saves a screenshot at the moment. The issue I'm having is that I would like to be able to save multiple screens without it overwriting the last screenshot which is what it seems to be doing at the moment, with filenames like:

Screenshot01.jpg
Screenshot02.jpg

Is this possible?