Salesperson leaves the company owing money–is his draw fair game for a deduction?

Q: “We are considering changing our compensation plan for account managers. Scenario: Employee will receive a monthly set salary in advance and also earn a commission on sales. However, if the employee’s commission does not equal the set salary, the company will deduct the difference of the commission from the salary that is paid in advance. If the employee should leave employment while owing the company the difference mentioned above, are there any laws that would prevent the company from deducting the owed amount from the employee’s accrued but unused vacation time that would be paid out at the time of the resignation?” – M.J., Oklahoma