Multiple Checkbox Lists, item can only be selected in one list

I have a selection of categories. I will have one or many textareas on a page. Each textarea can be assigned to one or more of each category. Each category can only be assigned to one textarea.

This is purely conceptual as this point, no code written yet. I'm thinking each textarea would have a jQuery checkbox list. The page starts out with a single textarea and it's related checkbox list. All items in the list are selected. User chooses to add another textarea (with a checkbox list). All items in the second checkbox list are disabled, as they are already assigned to textarea 1. As I uncheck items in the first list, they become enabled in the second list and can be checked.

Thoughts? Good or bad UI? How hard would this be to code?