Possible? Selling items in groups of 10 while selling other items as singles

I've been all over the forum and haven't found a solution to my scenario, here goes:

Scenario - cart selling greeting cards in shopper-selected boxes of 10 as well as other merchandise - t-shirts, music downloads, etc. There is going to be over 100 card designs and users will be able to choose which card design they want to put into their boxed set but **must **order the cards in quantities of 10. But at the same time they can order a single t-shirt or download.

I would like to create each card design as a product rather than as an attribute of a single product so it is easier to browse the designs and their captions and offer better expansion options should they decide to sell cards individually in the future.

I would appreciate any suggestions on how to approach this. Perhaps I should modify the Minimum Number of Items module to check what category the item is in and to activate if the cart contains cards?

Thanks!
Alane

To force quantities in increments of 10 (for example, 10, 20, 30, 40 cards at a time) you would set "Product Qty Units" to 10. This is done on the page where you create/edit your product.

If the customer orders anything other than in increments of 10 an error message will appear asking the customer to "Please update your order... Quantity Units errors - You ordered a total of: 12 Units:10" (or something like that...I changed the wording a bit on my site) I think you might want to change that last part it to say something like "Sold in Units of ".

This setting is done on an individual product level and will not prevent buying another product (such as your t-shirt) individually or at some other preset increment.