Plugin request: simple calendar with highlighted days

It might seem strange that a plugin for this doesn’t exist (and maybe it does), but I’ve been looking and looking, and the ones I find are way too complex.

What I need is a plugin that lets me display a simple calendar, like the one on this page, and lets me hook off/select which days are unavailable from within the WordPress admin area.

Maybe there are similar plugins out there that I could edit to fit my needs?

Thanks.