var currentParameter = "NO3";
        if (document.images)
        {
                var NO3image = new Image(120,20);
                NO3image.src =
			"images/NO3button.png";
                var NO3selimage = new Image(120,20);
                NO3selimage.src =
			"images/NO3selbutton.png";
                var NH4image = new Image(120,20);
                NH4image.src =
			"images/NH4button.png";
                var NH4selimage = new Image(120,20);
                NH4selimage.src =
			"images/NH4selbutton.png";
                var PO4image = new Image(120,20);
                PO4image.src =
			"images/PO4button.png";
                var PO4selimage = new Image(120,20);
                PO4selimage.src =
			"images/PO4selbutton.png";
                var NO2image = new Image(120,20);
                NO2image.src =
			"images/NO2button.png";
                var NO2selimage = new Image(120,20);
                NO2selimage.src =
			"images/NO2selbutton.png";
//                var Siimage = new Image(120,20);
//                Siimage.src =
//			"images/Sibutton.png";
//                var Siselimage = new Image(120,20);
//                Siselimage.src =
//			"images/Siselbutton.png";
                var TDNimage = new Image(120,20);
                TDNimage.src =
			"images/TDNbutton.png";
                var TDNselimage = new Image(120,20);
                TDNselimage.src =
			"images/TDNselbutton.png";
                var TDPimage = new Image(120,20);
                TDPimage.src =
			"images/TDPbutton.png";
                var TDPselimage = new Image(120,20);
                TDPselimage.src =
			"images/TDPselbutton.png";
                var Climage = new Image(120,20);
                Climage.src =
			"images/Clbutton.png";
                var Clselimage = new Image(120,20);
                Clselimage.src =
			"images/Clselbutton.png";
                var SO4image = new Image(120,20);
                SO4image.src =
			"images/SO4button.png";
                var SO4selimage = new Image(120,20);
                SO4selimage.src =
			"images/SO4selbutton.png";
	}

function setParameter(newParameter)
{
	if (newParameter == currentParameter) return;
	if (currentParameter == "NO3")
	{
		document.images["NO3image"].src =
			NO3image.src;
	}
	if (currentParameter == "NH4")
	{
		document.images["NH4image"].src =
			NH4image.src;
	}
	if (currentParameter == "PO4")
	{
		document.images["PO4image"].src =
			PO4image.src;
	}
	if (currentParameter == "NO2")
	{
		document.images["NO2image"].src =
			NO2image.src;
	}
//	if (currentParameter == "Si")
//	{
//		document.images["Siimage"].src =
//			Siimage.src;
//	}
	if (currentParameter == "TDN")
	{
		document.images["TDNimage"].src =
			TDNimage.src;
	}
	if (currentParameter == "TDP")
	{
		document.images["TDPimage"].src =
			TDPimage.src;
	}
	if (currentParameter == "Cl")
	{
		document.images["Climage"].src =
			Climage.src;
	}
	if (currentParameter == "SO4")
	{
		document.images["SO4image"].src =
			SO4image.src;
	}
	if (newParameter == "NO3")
	{
		document.images["NO3image"].src =
			NO3selimage.src;
	}
	if (newParameter == "NH4")
	{
		document.images["NH4image"].src =
			NH4selimage.src;
	}
	if (newParameter == "PO4")
	{
		document.images["PO4image"].src =
			PO4selimage.src;
	}
	if (newParameter == "NO2")
	{
		document.images["NO2image"].src =
			NO2selimage.src;
	}
//	if (newParameter == "Si")
//	{
//		document.images["Siimage"].src =
//			Siselimage.src;
//	}
	if (newParameter == "TDN")
	{
		document.images["TDNimage"].src =
			TDNselimage.src;
	}
	if (newParameter == "TDP")
	{
		document.images["TDPimage"].src =
			TDPselimage.src;
	}
	if (newParameter == "Cl")
	{
		document.images["Climage"].src =
			Clselimage.src;
	}
	if (newParameter == "SO4")
	{
		document.images["SO4image"].src =
			SO4selimage.src;
	}
	currentParameter = newParameter;
}