Filtering by multiple selections at the same time

I have created a category table which I use in other tables in order to assign catgeries to items. One item may be assigned to mutiple catgeories, for example, an article that discusses Business Process Management may refer to BPM in the Projects and Retail and may also talk about BPM's impact on a company's Financials. I would then choose the categories of Projects; Retail; Financials and Process and assign them to that article.

Now I want to filter things in the Concatenate of Categories view but do this by being able to slection items with more than one category, for example, I may want articles with Projects and Financials, or naother time I may want Projects, Financials and Process. How do I do this? So far I only know how to get it to show one item by using: like "XXXXXX".

Thanks!