Big Fat Turnitin Grademark #Fail ?

I appear to have completely misunderstood how the Post Date setting in Turnitin GradeMark works. (Or have I? It's so confusing I can't be sure.) I thought that by setting the Post Date, students could view their feedback in GradeMark but not their mark until the Post Date is reached. However, this is not the case. Post Date only works when Anonymous marking is selected in the Turnitin assignment - which is not what I want (and I'm not sure if we can set that here anyway).

So is there anyway to separate feedback from marks in GradeMark other than making two inefficient passes though the cohort, once to add feedback and then again at a later date to add the mark?

A.J. Cann