Need a better definition as to when POs require authorisation

Our customer currently has a set-up whereby any POs above £10K require authorisation. If anything is changed on the PO such as approver or reference the PO requires approval in order to print again even though the values have not changed. Is there any way of being more specific on these authorisation rules so that we only need to approve again if there is a change to the value of the PO?