Remove Add Existing button

HideAssociatedViewButtons(['Add Entity Name'],['Add record ID']);

function HideAssociatedViewButtons(leadAreaId, buttonTitles)
{
var navElement = document.getElementById('nav_' + loadAreaId);
if (navElement != null)
{
navElement.onclick = function LoadAreaOverride()
{
loadArea(loadAreaId);
HideViewButtons(document.getElementById(loadAreaId + 'Frame'), buttonTitles);
}
}
}

function HideViewButtons(iFrame, buttonTitles)
{
if (iFrame != null)
{
iFrame.onreadystatechange = function HideTitlesButtons()
{
if (iFrame.readystate == 'complete')
{
var iFrame = frames[window.event.srcElement.id];
{
var LiElements = iFrame.document.getElementsByTagName('li');
for (var j=0; j< buttonTitles.lenght; j++)
{
for (var i=0; i< liElements.length;i++)
{
if (liElements[i].getAttribute('title') == buttonTitles[j])
{
lielements[i].style.display ='none';
break;
}
}

}
}
}
}
}
}