Smaller squashes, like butternut, patty pan, or acorn, can grow on a strong tepee or trellis, Viv. Big ones, like hubbard or banana, are better off on the ground, or in cloth slings attached to a very strong trellis. You can nip out the tip as long as it is already producing fruit, but that will stop further fruit production for a few weeks--sometimes a good thing, with the larger varieties.

thanks T - its a small thing called munchkin

I'd just put three stout stakes in the pot, tied together at the top to make a tepee, and let the vine grow up and down as it pleases. If the greenhouse has plexiglass panes, or is made with plastic film, I'd put the plant in partial shade when first it's moved out, to keep it from getting ultraviolet sunburn.