The inexperienced pilot was on a solo visual flight rules (VFR) navigation exercise from Essendon, tracking via Moorabbin, Kyabram, Calivil, Melton South and returning to Essendon. After passing Kyabram the pilot observed cloud developing to the west and decided to amend his route. Before reaching Bendigo he turned south and, as there was cloud ahead, the aircraft was climbed to 4,000 ft, on top of cloud. The pilot then established communications with Melbourne Radar Advisory Service (RAS) and requested navigation assistance. A short time later, RAS advised the pilot that he had just passed Trentham. At about this stage the aircraft was inadvertently flown into cloud. The pilot experienced control difficulties, because of the turbulence in the area, and reported to RAS that he was "descending quite fast", but that he was trying to climb. Another pilot advised the pilot of VH-JAC to "just keep your wings level." Less than a minute later, the pilot of VH-JAC reported he was upside down and going to crash. The aircraft broke out of cloud, below the cloud and close to the ground, in a steep nose-down attitude. The pilot managed to regain control and avoid trees. Visual flight was then continued and the aircraft was diverted to Bacchus Marsh where a landing was made.