Page Template Custom Options

Hi all,

I have a little question. I am making a template that uses custom page templates. Now i ran into a problem. I want to create a page with a intro text and blog posts that come from a certain category. When a user creates a new page, I want them to be able to select the category from witch the posts are shown. Kinda like a drop down box with category’s from where they can select the category they want. Does anyone maby knows a tutorial where I could learn how to do this ?

I mean something like this: Image

I already searched google but I could only find tutorials on how to make a template options page.

Thanks in advance,
Bob