What is the matter with <div>'s scrollHeight

[quangnd412]

Hi guys,
I want to scroll a DIV. When the DIV scroll the the bottom, it will scroll upward and vice versa. The problem is: When it scroll to the bottom, odivScrollBarStockInfo.scrollTop can not be increased any more but it is still less than odivScrollBarStockInfo.scrollHeight!!!
In order to make it work, I have to write a funny code (bold lines).
What is the problem here?

Please look at this code

function _scrollTables()
    {
        var scrollTop = odivScrollBarStockInfo.scrollTop;
        scrollTop += scrollStep * scrollDirection;
 
        if(scrollTop < 0)
        {
            scrollDirection = 1;
        }
        else if(scrollTop > odivScrollBarStockInfo.scrollHeight)
        {//this never can be reached!!!
            scrollDirection = -1;
        }
        else
        {
            odivScrollBarStockInfo.scrollTop = scrollTop;
            //funny code
            if(odivScrollBarStockInfo.scrollTop != scrollTop)
            {
                scrollDirection = -1;
            }
        }
       setTimeout("_scrollTables()",scrollDelay);
    }

[acoder]

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