Fixed quantity and discounts???

[SanchoPanza]

We have products which we sell in certain boxes. Each box contains a certain number of items. Of course, the bigger the box the less price the customer pays. For example, we have boxes:
10 items - $price 1;
20 items - $price 2;
50 items - $price3;

So, what I can do with Zen is:
1) I can make one category and insert there products like box10, box20, box50 and give each a certain price;
2) I can make one product and use qty discounts, BUT I don't know how to make the fixed quantities and discounts, so the customer can't, for example, choose 11 or 21 items etc.??

Please help.

[swguy]

You will want to use attributes to indicate the count and price the attributes.