Any chance to update a UIProgressView while NSKeyedUnarchiver?

Question

in my app, I save arrays in core data with NSKeyedArchiver. Then, I use the following code when the data is needed (to feed Core Plot) :

dispatch_queue_t backgroundQueue = dispatch_queue_create("com.mycompany.myqueue", 0);
dispatch_async(backgroundQueue, ^{
    dataForPlot = [NSKeyedUnarchiver unarchiveObjectWithData:self.measure.dataArray];
});

This works great ! But when the dataArray is big it can't take a few seconds to unarchive. Is there any way update a progressView bar while unarchiving ? Thanks in advance.