Automatically Calculating Queue Hours

I don't know if it's possible, but asking for a colleague.

We have a pretty flexible production schedule and run times less than a couple of days. So, our goal is to have all raw materials in house four weeks prior to the recommended completion date. We've been putting queue hours to handle this, but are realizing that we are adding too much time. We are wondering if there is any way to handle this where we can calculate the queue time on the individual routers.

If there isn't a systematic way, does anyone have a "quick" formula calculation outside the system so that we can adjust the queue hours accordingly on the routers?