Why don't you use T Code TBEX which provides excel upload utility to update exchange rates en mass and updates the Table TCURR only and you do not need to have TR created for the same. It also saves you the hassle of updating manually individual rows in OB08. If you are from Security team as you mentioned in your communication, your FI Consultant should easily be able to use the above t code and do this as a process improvement using excel upload.
Thanks & regards
Sanil Bhandari