In an existing application which I am modifying an auditlog which records values before and after the changes to the fields.Currently audit log is done by calling a generic function, i.e.

x = auditlog('table','key','keyvalue')

For a few fields in one table a comment also has to entered if the field changes. I do not want to rewrite the function since I do not know how many comments I will have and I do not want to break existing code. What is best way of doing this. Some possiblities I condidered,
1. add some form properties to hold the comments but can I use them in the function with out explicitly passing then to the function, if so how?
2. create public variables that get released as soon as I return form function, do not care for this one if I can avoid it.
3. other ideas?