I have a trouble. Consider a task 'developing software'. This task has 1000hrs of work. A single developer might work for 1000hrs, or two for 500hrs. Duration, in a standard 5d with 8hr/day, is 125 day with one developer, or 62.5 with 2 developer. However, there's a third resource, the team leader, that need to spend 5% of total work on the task, but should not affect the duration. In MS Project, when I insert this third resource, the task duration is recalculated and work is spread on this resoure, like 475hr for each of two developers and 50 for the team leader.
Is there a way to prevent this?