How to update Prorate Convention and Retirement Convention in Asset categories

Hi,
We defined new 'Prorate Convention' in our system. There are lot of Asset Categories in our system and we need to update 'Prorate Convention' and 'Retirement Convention' in the Asset Categories form? Is there any way to update all our 'Prorate Convention' and 'Retirement Convention' in the Asset Categories at once? Updating each and every Asset Category will take lot of time for us. So can anyone suggest the best and easy way to update all of them at once?

Thanks
VT