Redmine

Hi, see the screenshot. This is a typical time tracking report on a project. I'd like to do the following:

1) Set the filter to automatically default to a date range to the previous month.
2) Add a new field which represents the total "bought" time our client has. I know this can just be added as a Project field.
3) Display, in addition to "Spent Time", the new "Purchased Time" field, and another value that is the different of the two called "Remaining Time".

As mentioned, I think adding the "Purchased Time" field is a peice of cake, but getting that field to display on the page, is there a plugin for this or would I have to develop my own? What about setting the date filter to the previous completed month?