Get progress information from ObjectTypeOperations.RefreshExternalObjectType

We have a VAF function (TaskProcessor) that triggers refreshes of external object types in an interval.
Now we face the problem, that if it takes longer than the interval to finish a refresh, the old refresh is aborted and restarted. We would like to check the progress of the refresh and only start a new refresh when the previous one is done.
We appreciate any help and a code snippet would be great.