Yes. Use
http://nldc.interfix.net/calculator and scroll to the very bottom.
Basically, the Start (input) numbers will be the exact speed of the train in Meters Per Second. So figure out how fast its going in MPH, then use that webpage to convert it.
Do the same for the VERY last piece of track. Be as exact as you can, then, when you get the m/s numbers, add 0.5 to them. It tends to be a little more accurate. I sometimes add an entire 1.0 to them.
Input the numbers, set your filter somewhat high (40 and larger) and start Heartlining!
EDIT- Also, if you are trying to heartline a complex element, use MORE verticies. The more you use the more accurate the banking and heartlining is. Ive seen some people use very few segments and get crappy results.
Example: Most Zero G's youll want to contain at LEAST 32 for a good roll free of any problems and heartline rolls you may want more. Just remember, your original track needs to be very good to use those higher numbers as it will produce the most accurate results of your original track, just heartlined.