"width tool" and paintbrush strokes???

Hello Folks,

I drew a cured line with the brush tool in illustrator CS5, but when I select the new "width tool" to change the width, it doesn't work.

What am I missing?

Here are my steps:

1. Select the paintbrush tool

2. Draw something

3. Select the "width tool"

4. Try to change the width but it won't work.

Since I draw with the paintbrush tool, the "width tool" can be very handy if I can get it to work.

Thanks!