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;
} 
}