Opening a project file with a jar file?

If you have a program(as a jar) that makes a project with a unique extension, and you want to be able to open the project file with the jar file, how would you do that?

 

You need to associate the extension to a file type, which points to, say,
"C:\JRE1.6\bin\javaw.exe" -jar program.jar %*
or, if that doesn't work,
"C:\Program Files\Java\j2re1.4.2_04\bin\java.exe" -jar "%1" %*
which also opens a command window, but seems to take parameters better.
You would replace program.jar with your program, and the path to javaw or java would differ on different installations. I got those 2 examples from this page:
http://stackoverflow.com/questions/394616/running-jar-file-in-windows
which also has instructions on how to do this.