“Employment” does not include service not in the course of the employing unit’s trade or business performed in any calendar quarter by an employee, unless the cash remuneration paid for such service is fifty dollars ($50) or more and such service is performed by an individual who is regularly employed by such employing unit to perform such service. For the purposes of this subdivision, an individual shall be deemed to be regularly employed by an employing unit during a calendar quarter only if on each of some 24 days during that quarter or the preceding calendar quarter such individual performs for such employing unit for some portion of the day service not in the course of the employing unit’s trade or business.