Implement a trigger behavior for C-ISAM files. Is it possible?

I would like to check the possibility to implement a trigger behavior using COBOL NetExpress 5.1 for C-ISAM files.

There is a set of Legacy COBOL programs that opens lots of BOOKS and C-ISAM files (IDX3) and I am trying to do a non intrusive approach to update data on my database when the C-ISAM file is altered (by update or insert).  If something like that could be done I would not need to change all the codes of my legacy.

I am not closed in this approach.  
I am open to suggestions.