function myChgPic(myPicURL){
   document.images["myBigImage"].src = myPicURL;
}
function myChgPic2(myPicURL){
   document.images["myBigImage2"].src = myPicURL;
}
function myChgPic3(myPicURL){
   document.images["myBigImage3"].src = myPicURL;
}
function myChgPic4(myPicURL){
   document.images["myBigImage4"].src = myPicURL;
}