Batch Rename

I would like to copy a group of files (e.g., XYZ_R1G) with a batch process and rename them, but I would also like to replace the last letter from the original file names (G) with new letter (e.g., XYZ_R1E). Is there a way to do this with a batch process? So far I have only been able to find a way to add the letter to the original when I copy files with my batch process.