UI change vs. programmatic change

[ScottBell]

Using Qt 4.7.3 and Designer, I placed a spin box in a group box.
In code, when a user makes a change, the value is sent away. When a reply comes back the spin box is written again.
Sometimes an external value change arrives asynchronously.

void MyGroupBox::on_MySpinBox_valueChanged(double d)
{
    // (other code)
    emit(signal_MyMessage(d));
}
 
void MyGroupBox::slot_MyExternalValue(double d)
{
    // (other code)
    ui->MySpinBox->setValue(d);
}

void MyGroupBox::on_MySpinBox_valueChanged(double d)
{
    // (other code)
    emit(signal_MyMessage(d));
}

void MyGroupBox::slot_MyExternalValue(double d)
{
    // (other code)
    ui->MySpinBox->setValue(d);
}

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The only relevant signals from a spin box are "editingFinished" or "valueChanged". EditingFinished isn't triggered by the buttons.
I've fiddled quite a bit but can't find a direct way to distinguish the source of the change.
The abstract spinner and other base classes can see mouse presses and other events, but I'm stumbling over the fact that Designer does all its work from within the group box with "ui->".
Sorry this seems like a common programming thing to want to do, and likely another case of C++ ignorance--patience, please.

Thanks, Scott