You can't do this.
This feature exist's in Moodle's assignment module, but has never existsed in the quiz. Would be a nice addition if anyeone ever wanted a programming challenge.
Quiz
Importing Individual Response Grades back into the 2.5 Quiz
دا بحث کولپ شوی دی نو تاسو نشئ کولی دې ته نور ځواب ورکړئ.