if (document.images) {
  img1on = new Image();           
  img1on.src = "Images/1_on.gif";  
  img1off = new Image();           
  img1off.src = "Images/1_off.gif";
  img1sel = new Image();           
  img1sel.src = "Images/1_sel.gif";

  img2on = new Image();           
  img2on.src = "Images/2_on.gif";  
  img2off = new Image();           
  img2off.src = "Images/2_off.gif";
  img2sel = new Image();           
  img2sel.src = "Images/2_sel.gif";

  img3on = new Image();           
  img3on.src = "Images/3_on.gif";  
  img3off = new Image();           
  img3off.src = "Images/3_off.gif";
  img3sel = new Image();           
  img3sel.src = "Images/3_sel.gif";

  img4on = new Image();           
  img4on.src = "Images/4.gif";  
  img4off = new Image();           
  img4off.src = "Images/4.gif";
  img4sel = new Image();           
  img4sel.src = "Images/4.gif";

  img5on = new Image();           
  img5on.src = "Images/5_on.gif";  
  img5off = new Image();           
  img5off.src = "Images/5_off.gif";
  img5sel = new Image();           
  img5sel.src = "Images/5_sel.gif";

}

function imgOn(imgName) {
  if (document.images) {
    document[imgName].src = eval(imgName + "on.src");       
  }
}

function imgOff(imgName) {
  if (document.images) {
    document[imgName].src = eval(imgName + "off.src");        
  }
}

function imgSel(imgName) {
  if (document.images) {
    document[imgName].src = eval(imgName + "sel.src");       
  }
}