It’s not possible to get another command’s message from a command without using the Nightbot API.
If you are just trying to do a win/death counter, this post has a guide: Some sort of counter to track deaths that viewers can view but not change and maybe a way to reset
If you want to store/retrieve/change any type of text, you can use this quote system: [CustomAPI] Quote system.
If you go into detail about the command you’re creating, I may be able to give more specific instructions.