Enable Riboon Button for specific list and single item selection

<CommandUIHandlers>
<CommandUIHandler Command="ListDocumentMerge_Test_Button" CommandAction="~site/_layouts/ListDocumentMerge/DocumentMerge.aspx?List={ListId}&ID={SelectedItemId}"
EnabledScript="javascript:function singleEnable() {
var items = SP.ListOperation.Selection.getSelectedItems();
var ci = CountDictionary(items);
var listId = SP.ListOperation.Selection.getSelectedList();
if (ci == 1 && listId == '{B8701B6B-8CB7-4105-852F-4C685F580A63}')
{ return true; }
return false; }
singleEnable();" />
</CommandUIHandlers>