Karen - I'll give you my thoughts, for what it may be worth. Melons, cantaloupes, and cucumbers can be done no problem, because I grew those last year. I think I would plant the pole beans against their own trellis, because those things are really hard to confine to an area of trellis - once they really start growing. The butternut squash would probably be quite difficult, but the pumpkins are possible. I'll try pumpkins this year for the first time (3 varieties on 6 feet of trellis), and see how it goes.

EG

Here is a link that might be useful: EG's Garden Blog

If they are 4ft wide you can easily fit 2 crops per trellis, even three if you wanted.
I currently have four 5 ft trellis (they overlap the box by 6" each end for more space):
1. pole beans, bon bon squash, tomato, tomato
2. tomato, peas, peas
3. pumpkin, cukes, raven squash
4. watermelon, watermelon, raven squash

I ended up having to add some things for family so my setup is a bit haphazard. Beans are good companions with cukes. Or you may want to use a lighter crop with a heavier crop so as not to overload your trellis if it is just netting.

I only got one tiny pumpkin from my vine last year, even though I went out and hand pollinated every female flower I saw. It probably needed more water than I gave it.

I have a box 28" x 84" x 12" deep that I am setting up for trellis plants. I have planting pole beans, canolope, watermelon, and squash in this box. Would I plant the seed in the back 12 x 12 space leaving the front space empty?

Lowraine,
You can plant them either way. I actually planted my beans some in the front and some in the back to make the most of that square. If you want to use the front for other crops (i put herbs in the front alot) then planting it in the back would give it some space :) .