Help: even rounded bend

I am looking to have a bend like this -> http://juicyonline.com/bend.gif but rounded on the inside, not 90 degree angle like it is now, how would I do this?

Use the rounded rectangle Custom Shape Tool.

Stroke the path with a hard-edged brush at the width you desire.

There are other ways, as well....

Or a gaussian blurred channel selection.... still, u gotta go with the vector.