Customize the background/border colors of a grouped table view using the solution of a previous post

I've read this post : How to customize the background/border colors of a grouped table view cell?

And I want to display a background cell. So I'm trying a use the previous post in the tableView function willDisplayCell.

No matter what I do, nothing is working. Could you help me out ? (My cells are 50pt high.)

Thanks

That question was posted two and a half years ago? for OS2 and then OS3. Probably not valid for OS4 or OS5.

An Apple engineer told me not to override drawrect like this as it was a "hack" and would likely break in a future OS version. So I would avoid doing that.