An approaching front was causing the wind to swing from a 45 degree headwind/crosswind to a 45 degree tailwind/crosswind from the left. Although the pilot reported that he considered that the conditions were not suitable, he decided to attempt a takeoff as he felt there was a pressing need to carry out a survey of his property. Just prior to lift off, the aircraft veered to the left and the nosewheel entered a soft area at the side of the strip. The nosewheel broke off and the aircraft cartwheeled across the paddock. The pilot had completed a rotorcraft pilot's course, consisting of 10 hours of instruction, and the first 10 hours of post course consolidation. However, the pilot had very little experience at operating a rotorcraft in fluctuating crosswind conditions. The loss of control was probably the result of a sudden wind change during the latter part of the takeoff roll and pilot inexperience.