Parsing stored proc/sql code

I've been asked to write a script to examine new stored procedures to see if
they do any writing (i.e. delete, insert, update) to the database, or,
recursively, if they call any stored procs that write to the database. I
can't just do a simple grep but also have to ignore comments and quoted
strings.

Before I embark on this task, I wonder if anyone's ever done anything like
this (even part of it); I'd hate to reinvent the wheel.

Thanks,

Steve