The PercentCompleted property returns the percentage of the task that is currently complete.
Task object
Long
Read/write
Although the data type for the PercentCompleted property is Long, applications should set its value in the range zero to 100. When a task is marked completed, the CompletedDate property should be set to True and PercentCompleted set to 100. The exception to this rule is for AutoDone tasks, which are complete at their end date, regardless of the CompletedDate or PercentCompleted property settings.