@mehlikamerve didn’t specify whether his task is to produce a design model with nice crisp folds, or a photorealistic model with the sort of folds you get in leather. If the latter, then nurbs are not a good choice, but the new Subd features in R7 are much more amenable.
Guidelines (a scaled series of rectangles, with every second rectangle rotated 90 degrees)
can be overlaid with a Subd box, creased along the outside edges to give a sharp outline and scaled to fit the end rectangles before subdividing to give the same number of edges as folds. Thne pushing the vertices to the guide rectangle corners, followed by filleting the longitudinal edges and adding smaller fillets along the edges matching the rectangles. And then some more edges interspersed so the the straight lines can be tweaked into slight curves. Leading to something like this:
It needs quite a lot more tweaking, but the promise is there.
Regards
Jeremy