one of the documented procedures in this installation of the ACS
mv_user_charge_replace_comment   user_charge   new_comment
What it does:
Takes a user charge data structure (actually just a list) and replaces the comment field (at the end); useful when there is a separate field for an admin to type an arbitrary comment.
Defined in: /web/philip/tcl/ad-member-value.tcl

Source code:

    set user_id [lindex $user_charge 0]
    set admin_id [lindex $user_charge 1]
    set charge_type [lindex $user_charge 2]
    set charge_key [lindex $user_charge 3]
    set amount [lindex $user_charge 4]
    return [list $user_id $admin_id $charge_type $charge_key $amount $new_comment]