how to modify or move the clipping box?

[gcutt]

How does a user modify an existing clipping box (bounds, extent and location) such as the one that appears when IDV is first launched, showing the default background map (coastlines) with a clipping box that bounds the U.S?
I have changed the horizontal scale, but that only shifts the graticule marks on the border of the box. How do I move the box?
Thank you.