need a help about the gridpanel`s store refresh

[matjumbo]

i did a gridpanel,want to keep the scrollbar`s state when the gridpanel refresh.
i can get the scrollbar`s top,left when the store beforeload use 'getScroll() ',and save it to store like 'store.scrollsObj'
then i did code in the event 'load',

var showPanle = tab.getGridEl().down('.x-grid3').down('.x-grid3-viewport').down('.x-grid3-scroller')
showPanle.scrollTo('top',store.scrollsObj.top+10);
showPanle.scrollTo('left',store.scrollsObj.left+10);

when i break debug it ,i find it can do ,but when the gridpane fresh over the scrollbar also go to left:0,top:0
why?
shoud i take another event?