zoom hidden vertical scrool bar ?

Hello, I need a bit of help. My goal is to put some Javascript code on a click event of a hidden button that is executed on form:ready

with btnHidden.executeEvent('click').

The code should zoom the pdf based on browser plugin width and hide panes a show Single Page Continuous

I found that the 2 instruction do almost all but there a defect for me: i also need to show the vertical scroolbar

event.target.viewState = {overViewMode:5};      //Hide Panes
event.target.viewState = {pageViewZoomType:2};  //Single Page Continuous

Can you please help me ?

Thank's in advance

   Alberto

P.S.

Sorry for my bad english