Thanks, here the modfied code selecting only objects in the same group.

/* Extend selection to same names, check ownerGroup */
var names = new Array();
var objs = moi.geometryDatabase.getSelectedObjects();

for (var i = 0; i < objs.length; ++i) {
var obj = objs.item(i);
if (obj.name != '' && obj.ownerGroup) {
names[obj.name + obj.ownerGroup.id] = true;
}
}

objs = moi.geometryDatabase.getObjects();
for (var i = 0; i < objs.length; ++i) {
var obj = objs.item(i);
if (obj.name != '' && obj.ownerGroup && names[obj.name + obj.ownerGroup.id]) {
obj.selected = true;
}
}



/* Extend selection to same names, show hidden objects, check ownerGroup */
var names = new Array();
var objs = moi.geometryDatabase.getSelectedObjects();

for (var i = 0; i < objs.length; ++i) {
var obj = objs.item(i);
if (obj.name != '' && obj.ownerGroup) {
names[obj.name + obj.ownerGroup.id] = true;
}
}

objs = moi.geometryDatabase.getObjects();
for (var i = 0; i < objs.length; ++i) {
var obj = objs.item(i);
if (obj.name != '' && obj.ownerGroup && names[obj.name + obj.ownerGroup.id]) {
obj.hidden = false;
obj.selected = true;
}
}