use Butler rule to populate iteration start and end dates

[RogerK]

hi there, we use week as Iteration basis in Trello and would like to auto populate current Monday as Iteration Start Date (custom field) and current Friday as Iteration End Date (custom field).  I believe this is basic business scenario.  Our cards are auto created with the email to board function.  However, there are no "current Monday" nor "current Friday" dates of the week in the Butler rule.  Can these options be added to the Butler rule or any suggested workaround ?