Sure.
1. get a list of all the members in the dataset (LISTD dsn M) into an OUTTRAP
2. walk the list (probably with PULL) selecting only members like MADDDM*
3. for each such, generate the desired new membername and issue { address TSO "RENAME" dsn"("mbr") ("newmbr")" }
There are some potential problems with this method. For one, some of those members may be aliases or have aliases and those members will have to be handled manually, or you will have to write lots more code.
Frank Clarke
Tampa Area REXX Programmers' Alliance
REXX Language Assn Listmaster