Attached is a very simple macro that will:
1) start a sketch on the front plane
2) sketch a center rectangle and prompt for dimensions
3) create a midpoint coincident relationship between the base line and origin
4) prompt with the option to extrude the sketch.
It's a simple macro but as a beginner level macro user it took me way too many hours to find simple examples that allowed me to create it so I thought I'd share it a maybe save another new user some time.
prerequisites: part document open
the zip file also contains a bitmap for the toolbar.