Bill, I would say the way you did it is the correct solution. Defining the prompt in the prompt manager makes sure that EG has the prompt available for use throughout the project. Getting those values used in the appropriate spot, and getting the appropriate prompt window, comes from associating the prompt with specific tasks, queries, or programs.
I agree it is a little work, but think about how much time you're saving down the road by getting the prompt rather than having to manually edit the code each time!