I have 4 files : A, B, C and D

File A just is a menu in which you can choose to open file B, C, or D. It
handles closing, saving and opening the files.

File C contains links to file B and file C contains links to C and B.

What I want to establish in file A, the menu file, is :

If a user leaves file B and opens file D, the menu should check whether file
C is older than file B. If so, the links in file C must be updated whithout
opening file C and before opening file D.

How do I manage that?

Thanks in advance,

Frigge