var oExt;
oExt = pMe.Pm("/data/#vars/Temperature/#ext/al");
// or
oExt = pMe.Pm("/data/#vars/Temperature").Extension("al");
// or
oExt = pMe.Pm("/data").Item("Temperature").Extension("al");
oExt.Min1 = 0;
oExt.Max1 = 100;
oExt.RefreshState();