Possible to make a specific host get the least priority?

I mean if there are hosts A,B,C, and D, can I make OpenWRT give D the least priority? That is, when the WAN speed is 100 and A wants 40 and B wants 40, D gets 20. If A wants 90 and B wants 50, then D gets 0.

You mean QoS?

Yes...but I lost you at the 90+50 portion.