rectangle - stretch/shrink width by dragging using javascript?

[quadrant6]

A graphic best illustrates the idea, which is pretty basic:



I'd like to have a rectangle which the user can resize <-width only-> by dragging on either side

I've seen drag and drop classes but they seem like overkill and yet I'm not easily able to pull out just enough to fo this.

does anyone know of a simple class or way of achieving this?

[MikeFoster]

Here's a quick demo that should at least illustrate the basic technique.