Configure working directory of Scala worksheet

I would like the working directory for Scala worksheet (and the Scala interpreter) to be the Eclipse project path rather than the Eclipse installation directory. How can I (non programmatically) achieve that?

I know that I can use System.setProperty("user.dir", "..."), but IMHO that does not belong in the code. Further, it does not seem to work:

object ScratchWS {
  System.setProperty("user.dir", "C:\\")          //> res0: String = C:\adt-bundle-windows-x86_64-20130219\eclipse
  new File("putty.exe").exists()                  //> res1: Boolean = false

  new File("C:\\putty.exe").exists()              //> res2: Boolean = true
}