EWR-COflyer,

For the itinerary I posted above, I actually just punched in EWR-MEM, MEM-ATL, ATL-MEM, MEM-EWR... I set the airline to Northwest only and maximum possible number of options, I just happened to pick the one that routed through DTW. I don't think it really matters what you punch in. I think the computer (ITN or other booking enginers) takes the itinerary you want and tries to match it to the lowest fare rule, applies it, adds taxes/PFCs and spits out the total.

I am not sure what you are doing to get that insane price... did you try the dates I slapped in above and the specific flights? They were the ones with K availabilty although I am sure there are others. Yeah, just make sure K doesn't have a 0 beside for each and everyone of your segments (e.g. for EWR-DTW-MEM: make sure EWR-DTW has K and DTW-MEM has K). Also, make sure you don't go through any other city other than what's listed in the fare rules or go back through a destination you've already been through (e.g. EWR-DTW-MEM-DTW-ATL would not be allowed)

Oh, I see why you want to route through IAH now... but for some reason, NW won't list non-stops between EWR-IAH or IAH-ATL (CO operated flights). I even looked on the Continental timetable and can't find a 777 operated on either of those routes, the biggest plane was the 764. So I can't figure out how to get a routing through IAH... but I hear ya, I'd take CO aircraft over NW's DC9s any day.

Oh I was playing around some more and I found another itinerary with an additional routing (although not through IAH).

Mar. 4 NW 11 EWR-DTW Dep 9:20am Arr 11:14am
Mar. 4 NW 1101 DTW-ORD Dep 11:15am Arr 12:14pm
Mar. 4 NW 477 ORD-MEM Dep 3:00pm Arr 4:38pm
Mar. 4 NW 822 MEM-ATL Dep 5:25pm Arr 7:47pm

Mar. 9 NW 827 ATL-MEM Dep 7:15am Arr 7:30am
Mar. 9 NW 290 MEM-ORD Dep 8:28am Arr 10:05am
Mar. 9 NW 178 ORD-DTW Dep 12:05pm Arr 2:27pm
Mar. 9 NW 1612 DTW-EWR Dep 5:05pm Arr 6:55pm

Price: $131.50
It sucks that most of these segments are on DC9s, but if you are looking for segements, there's 8 right there. For this itineary, I entered EWR-DTW, DTW-CHI, CHI-ATL and the same reverse routing

If you still end up with high fares, maybe you can try pricing either of the itinearies I've posted exactly (flight numbers and dates) and see if you can get the $131 fare...

Hope that helps a bit more.