Last Activity Time Vs. Modified Time

Last Activity Time Vs. Modified Time

I understand the intended differences between the above referenced Time Fields. I have also seen the following in previous Topics:

The activities and updates that will be recorded as Last Activity time:

    • Editing fields in a record
    • Adding & updating activities, i.e. Tasks, Events, Calls
    • Sending emails to leads and contacts
    • Adding & editing notes
    • Adding potentials & contacts under an account
    • Changing the owner of the record
    • Adding and deleting a record
      (This does not include deleting a record associated to the parent record.)
    • Closing a task
      (Not used for events as they are automatically moved under Closed Activities after the End DateTime.)
    • Deleting and restoring the records (individually or in bulk).

The activities and updates that will NOT be recorded as Last Activity time:

  • Mass operations such as Mass Update, Mass Transfer etc.
    (Except for the Mass Delete option.)
  • Editing contacts or potentials under an account will not be listed under the Account.
  • Deleting related lists under a record.
My problem is that the Last Activity Time Field is not accessible to the user. We have a variety of tasks and alerts that trigger off of time frames. Specific to this issue, we have an alert that triggers if a case is not modified for 30 days, but is still open. However, I find that in some of these cases we have users going in and adding Notes to the Case (Pending Customer, Vendor, etc.). 

Is there anyway that either the Modified date can be enabled to update on the addition of Notes, or that the Last Activity Date can be made available for workflow triggers?