There is no way to automatically open a document, neither a spreadsheet without having the user do something to open it (at least click a link).
What you could do is to show a popup in your spreadsheet with a link that would open that document.
This is quite simple to do from a spreadsheet script, please refer to this post and to the docslist documentation.(use doc ID
to access docsList.getUrl()
EDIT : following your comment, here is a possible way to automatically hide the popup, I included this in a full demo code.
function test(){
var id = "1cZCL7T-enU0yJZnCb0WM0NeqXDHjnnBUyvs98vsyzwU";// test document (shared in view only)
var Doc = DocsList.getFileById(id);
showURL('Open document named "'+Doc.getName()+'"',Doc.getUrl());
}
function showURL(nameToShow,href){
var app = UiApp.createApplication().setHeight(50).setWidth(300);
app.setTitle("Show URL");
var link = app.createAnchor(nameToShow, href);
app.add(link);
var handler = app.createServerHandler('hide');
link.addClickHandler(handler);// add serverHandler to the link itself
var doc = SpreadsheetApp.getActive();
doc.show(app);
}
function hide(){
var app = UiApp.getActiveApplication().close();// close the popup window
return app;// apply change
}