Scrolling a Selection Box Onload

I have page that is generated with a selection box with a size=7 clause
that contains some 30 options. When the selection box is generated with
the 10th option selected, the default display is to show options 4
through 10.

I want the box to appear with the selected option in the middle -- I
want it to display options 7 through 13 when option 10 is selected.

Is there a way to create a function that can be executed onload that
will "click" the down arrow in the selection control box 3 times? Are
there alternative methods to effect the default display?

Roger