The replication are FIFO queues, which means "first in, first out". Therefor there is no priority support in there. In your case I would add a second set of replication agents, which are normally not used (by doing the appropriate settings on the agent). For high priority replications implement a special function (either via workflow or directly connected to the UI), which replicates this page only via these second set of agents. As all agents are processed in parallel, and normally these special replication agents don't have any item in their queue, it should be pretty fast out. You need to make sure, that both of your users are not activating the same page, which could result in an unexpected behavior.