Is a Changelog possible in VBA?

[globalpontoon]

I have been playing around with a few things with a file I am writing, and would love to have a changelog element to it, for once I go live in the office.
I have managed to get the program to register all changes made to the document, list the address of the changed cell, list the user who made the changes, and detail either the formula or cell value of the changed cell depending on which change has been made.
The one thing I cannot figure out how to do, is to be able to record what the previous value was before the change.
If this cannot be done, then obviously there is no point in having the changelog in the first place.

So, I guess my question boils down to, is there a way of using a workbook_change, or worksheet_change event to record the previous value before the change, or is this a much more detailed API type call that I would need to look at.