Merge Duplicate Layer Names?

When using the "RENAME" command, and renaming layers, is there an easy way to avoid the "Duplicate new name specified." error?

Of course I can find the duplicate layer, purge it, then rename... but is there a faster way to force these layers to auto-merge?

Example:

Renaming SXXX_Demo to S100_Demo.

There is already an S100_Demo.

Can I force SXXX_Demo to join/merge with the S100_Demo layer?

Thanks very much in advance!