var imgDir = "/images/";

function OnSB(imgName) { 
    if (document.images && document[imgName]) {
       document[imgName].src = imgDir + "sb_on.gif";
    }
} 

function OffSB(imgName) {
    if (document.images && document[imgName]) {
       document[imgName].src = imgDir + "sb_off.gif";
    }
}

function OnB(imgName) { 
    if (document.images && document[imgName]) {
       document[imgName].src = imgDir + "b_on.gif";
    }
} 

function OffB(imgName) {
    if (document.images && document[imgName]) {
       document[imgName].src = imgDir + "b_off.gif";
    }
}

function ChangeImg(imgName,imgFile) { 
    if (document.images && document[imgName]) {
       document[imgName].src = imgDir + imgFile;
    }
}