Sorry guys...but random is random.
If you have a goal in mind -- a near-50/50 split -- then random selection is a poor choice with, say, 4 fields.
But, if you had 100 fields then random will get you pretty close and no one can claim an ulterior motive.
If you want a guaranteed even split, randomness does not make sense. In fact, it will take some real human intervention to make that work.
Excel - randomizing data for splitting farmland
