Dariocg --
My solution is based on two assumptions:
1. You are using the Professional version of the Microsoft Project desktop application.
2. You are linking all detailed tasks and milestones with Predecessors and Successors.
If you meet the two assumptions above, here is what you could do. Suppose the task in question is named Design and you have set a Duration value of 30 days. Immediately after the Design task, insert a new task named Design Safety, and set the Duration of this task as 30 days as well. Then link the Design task, the Design Safety task, and the following task with a Finish-to-Start dependency relationship. Click the Design Safety task to select it. In the Schedule section of the Task ribbon, click the Inactivate button to temporarily "cancel" the Design Safety task.
If the Design task starts going very late, you can reactivate the Design Safety task. Hope this helps.
2.
