[Groff] How to save the TOC from .TC to make changes on it?

[javier . gracia]

Hello, I'm using the .TC macro from the mm macros in order to 
generate a CONTENTS section. As usual, the result is good but
I want to make some changes on it.

Is there any way to save the groff source generated by this macro 
into any file so I can make some changes and print it separately?

I try to put some .tm "output this" into m.tmac inside the macro
definition to try to redirect what I want to standard error but
it's my first time dealing with macros and surely I'm making 
mistakes and there's a better approach.

Any ideas ? thanks,
Javi.

I'm using groff version 1.17.2 on debian Linux and modifying
/usr/share/groff/1.17.2/tmac/m.tmac

I got nothing on standard error.