I would create a nurbs plane, with maybe like 30 isoparms in both directions, and convert it to a soft body using the original nurbs plane as a goal. Then set per particle goal weights using either a ramp, or by hand, through the component editor, such that particles at the bottom of the curtain have a goal weight of 0.1 or so, and particles at the top of the curtain have goal weights of around 1.0. Then, connect the soft body to an air field, probably wind, and modulate the magnitude with an expression. I would use a sin, or cos function in the expression to smoothly change the wind's intensity over time. If you don't know how to do this, look in the Using Sets and Expressions Manual. It is a little confusing, but basically all you need to do is say something like.
air.magnitude = sin (time);
This way, the magnitude will change smoothly as the animation plays. Please, check with the manual for the proper syntax, because I don't have mine with me. I hope this helped. 
