How to prevent negative employee contribution for HSA

When an employee decreases their contribution, the new amount should not be less than the amount already contributed, as this can result in a negative amount being deducted from their pay. If the employee elects to reduce the contribution below the amount already contributed, the contribution should default to $0 or the system should display a valid range of amounts for the employee to choose from. Currently, the system allows the contribution to be reduced below the amount already contributed, resulting in a negative amount. This should be corrected to ensure the contribution defaults to $0 instead. Can this be achieved ?