Hi,
Unfortunately selecting "specific sorting" is not possible with "Product Slider" module.
"Product Slider" is one of our oldest module, i don't know how many years ago we released it, but we definitely need to update that module and add some new features to it.
For example, we have released a new module about 2 weeks ago, and specific sorting is possible with this new module, it is called "Modern Slider",
Attachment ScreenShot2013-12-06at3.13.00AM.png not found
For more into:
www.flexiblewebdesign.com/Virtuemart-Modules/Virtuemart-Modern-Slider-Products-by-Category-Tabs
Regards,
Support