Hi, ZhangJennie, thanks a lot for your answer!
I was recommended to use this tool: https://www.iar.com/iar-embedded-workbench/downloads/
You can see that it supports compiling for HCS12 board: "IAR Embedded Workbench for HCS12".
I have not tested it yet but, may be, we can develop in CodeWarrior 5.1 (just as an IDE) and then use this compiler.
Of course, if it works, you can tell me: "you are not using CodeWarrior 5.1". And you are right, since I would be changing its native compiler.
I repeat: I have not tested this yet. Will provide an update as soon as possible.
Thanks again and regards!
PC