File successfully read BallsInBox.xml
File saved successfully users/wee/BallsInBox.xml
Generating simulation file BallsInBox...
Compilation successful
Congratulations! The simulation was generated successfully.
Trying to run simulation BallsInBox...
Sorry! The simulation produced a run-time error.
strange after that i run again ok now............[/font][/color]

[color=blue][b][color=red]Qn:  How to construct a string or rod constraint on the balls ? [/color] [/b] [/color]

My thoughts:
Experiment 2 looks the best to modify from.