Require approval for changes to certain fields

We would like to be able to 'lock down' some fields unless there is approval to change them.

For example,

• Release date (or due date)

• Budget

Designated people in the company would be required to approve any changes to these fields.

Along with this, we would like

• Notifications when these fields are changed. The people who are interested in these notifications do not want to receive notifications about all the changes to releases or features in Aha!

• Reporting that can show changes to these fields over time