Adding time to an existing Task should take into account time already committed

Adding time to an existing Task estimate should take into account time already committed. Currently the additional time added to the Task estimate are spread over the full duration of the task. it should take adjust for time passed and hours expended

· Take total time estimated to complete the Task (original time + additional)
· Subtract how much time has been billed against it so far—that will give you the amount of time remaining
- Divide by the duration (e.g. number of weeks) remaining to get the time allocation for the resource for the task