Strict ordering for jobs

Hi,

Consider messages M1, M2, ... Mn, with each message having a feature x such that M1.x = x1, M2.x = x2, ..., Mn.x = xn..
Now consider another message Mz where Mz.x = x1

Given say, p consumers waiting for jobs, is it possible to enforce that Mz is strictly processed only after M1 has been processsed. Meanwhile M1, M2, ..., Mn can be processed in any order