Ubercart

I have a client who has just asked me whether her store (Drupal5, Ubercart 1.6ish) can handle a BOGO-type coupon. (Technically she wants a buy-two-get-one-free, but BTGOF does not really have the same ring to it.)

She uses coupons all the time, but can't figure out how to create this type of coupon. I can't, either, but I figured someone here has probably walked this path before.

Thanks!