( I don't have access to Chinese keyboard at this moment)
I actually don't know how to explain them in Buddhist terms though the distinction is very clear to me.
Desire is selfish and often pretentious too. It works around the ego, hence begets fen1 bie2 xin2 ("the dividing heart", "the distinguishing mind"). One can work very hard on his project with it, but he always desires the result. So the process generates a lot of miseries and sufferings especially when there is no result.
Will is universal, selfless and truthful. One works very hard with it too, but he is not after the result. There is a sense of "it should be done" in it. For instance, Li Ziqi on making videos, a minor activity, but she put her heart in it. The fame and profits later were only a by-product.
I have noticed that most people don't operate on Will. Yet the true, creative masters always do, for instance, people involved in the arts.
Hope my comment making some sense.
