Forms Data Controls :: Editable Drop Down List Within ListView?

I have a ListView that contains a lot of editable items. Every item has some values, like; item name, item price, item size and so forth. I would like to add another editable column which should be a drop down list. This should list which sizes the item is available at, like S, M, L, XL. Some item are only available in S and M, while other items may just have a standard size (meaning none of the above sizes). So for example if you are to add an item called polo shirt and its only available in sizes L and XL then you should be able to do that. And then at the front-end where the users surf the items it should be like that when a users sees this Polo shirt he should be presented with a drop down list where he is only able to select L and XL

I can't figure out how to implement this in the Listview and the database. I have mentioned that I want a drop down list to appear in the back-end, this is not a necessity, anything will do as long as the front-end is showing a drop down list with the choosen sizes.