Is this possible........yes.
Any easy way........kinda.
Here is the long and short of it......
There is a Visual Basic script that was written by Aussie Homebrewers that will do the conversion, but there several steps and it is not super straight forward and it is not perfect. In order to use the script, you must first export the ProMash recipe to a text file. This is done through the print menu. When you do this, you must make sure all boxes are checked else it will not work correctly. Next, you need to run the script and point it to your newly created text file. Then you will need to tell it where to save the .xml file that it will create. After the script runs it will tell you if it worked. Last, you will need to open the .xml file with BeerSmith. Make sure you test the script. I have found where there can errors if not everything is checked in the ProMash print screen.
The script can be found at http://www.beerxml.com/converter.htm
Cheers!