Using the Indexer Virtual Tool that Jack has provided, I would use the "Turn a blank to a finished size" function to create a taper by entering different numbers in the "Finish radius at start point of turning pattern" and "Finish radius at end point of turning pattern" options.
Then I would use the "Turn traditional flutes, spirals, or rings" function for the flutes, making sure to set the "Radius at Start point of turning pattern" and "Radius at Finish point of turning pattern" to match the taper you just created. (Note that this would be the start and finish of the flute and likely slightly different than the numbers entered for the original blank.)
Unless others have figured out some fancy trick, the Virtual Tool does not provide an option to taper the flutes to match the changing diameter of the blank. To the best of my knowledge, you would need ArtCAM or another similar program to accomplish tapered flutes.
In case it helps, here is the link to the Indexer Virtual Tool manual on the ShopBot web site:
http://www.shopbottools.com/files/SB...509Indexer.pdf