How to enable accept button when user complete crolled down than message

function checkScrollPosition(divFrame)
{

if (divFrame.scrollHeight - divFrame.scrollTop + 17 - divFrame.offsetHeight < 50) {
document.getElementById('<%=ButtonAccept.ClientID%>').disabled = false;
document.getElementById('<%=LabelScrollMessage.ClientID%>').style.display = 'none';

}
}

Thanks
Mahesh K. Shamra