var speed = 10;         
var max_opacity = 100;   
var min_opacity = 0; 
var do_step = 10; 
function change_opacity(obj,do_option)
{
   if(obj.doing)
    clearInterval(obj.doing);
   obj.doing = setInterval(do_option+"_alpha("+obj.sourceIndex+")",speed); 
}

function down_alpha(obj_index)
{
   var obj = document.all[obj_index];
  
   if(obj.filters.Alpha.Opacity > min_opacity )
   {
    obj.filters.Alpha.Opacity += -do_step;
   } 
   else
   { 
    clearInterval(obj.doing);
    obj.filters.Alpha.Opacity = min_opacity;
    obj.doing = false;
   } 
} 
function up_alpha(obj_index)
{
   var obj = document.all[obj_index];
  
   if(obj.filters.Alpha.Opacity<max_opacity)
    obj.filters.Alpha.Opacity += do_step;
   else
   { 
    clearInterval(obj.doing);
    obj.filters.Alpha.Opacity = max_opacity;
    obj.doing = false;
   } 
}