My archive is 10 hours long, but I want to showcase my content in a player that only plays from 4 hours to 5 hours.

Build a player with two flashvar variables called startTime and endTime. Set initial values for these of 3600*4=14,400 and 3600*5 = 18000. In your player code, for your first play request, add a " &seek=”+startTime to your stream URL. This will start it off playing at the correct point. Adjust your control scrub bar so that it shows a duration of endTime-startTime and a current position of ( ns.time - startTime). Adjust your seek handler so that it calls seek(startTime + newSeekPoint) on the stream. For example, if your scrubber calls for a seek to what looks like the 10-minute mark (600 seconds), then you would issue a seek(14,400 + 600) = seek(15000). The last thing you have to do is monitor the ns.time and check if it is greater than endTime. If it is, stop the stream.