Cdn Payroll Additional Tax in Employee Tax Info

We have several part time staff who elect to have additional tax taken from their pay cheques.  When these employees have no earnings in a pay period we have to manually remove the additional tax in order to process the payroll otherwise the system will put the employee into arrears.  We do not want to pay over additional tax when there are no earnings.

Is there a way to tell the payroll cycle to ignore the additional tax when the employee has no earnings in a pay cycle?

As our list of employees who elect for this additional tax increases, the manual work and tracking is also increasing.  I'm hoping to find a way we can stop this manual effort.