function toggle_display(block_id, icon_id, plus, minus)
{
	var block = document.getElementById(block_id);
	var icon = document.getElementById(icon_id);

	if(block == null) return false;

	if(block.style && block.style.display && block.style.display == "none")
	{
		if(icon != null)
			icon.src = minus;
		block.style.display = "";
	}
	else
	{
		if(icon != null)
			icon.src = plus;
		block.style.display = "none";
	}
}