Modify the Mark Comments Value

I am looking to write a macro that periodically updates the "Mark Comments" field under the mail replies options.

I would like for it to update to something like this "On <today's date> I Wrote". Where the date is entered by the macro

I've got the periodic portion of the problem figured out but I can't figure out how to access and replace the field value. Has anyone ever tried this? Can this value be changed by VBA?