In Embarcadero C++ I need to code a yComboBox and XComboBox1, XComboBox2, etc. It should be any

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Question:

In Embarcadero C++ I need to code a yComboBox and XComboBox1, XComboBox2, etc. It should be any content put into the y input should not be found in any x inputs. How do I code that?

This code that I did is not working properly, it's not flagging it as error if I put the same input in y box and x box.

if (this->yComboBox->ItemIndex == this->XComboBox1->ItemIndex || this->yComboBox->ItemIndex == this->XComboBox2->ItemIndex || this->yComboBox->ItemIndex == this->XComboBox3->ItemIndex) {
complete = false;
}
else {
complete = true;
}
return complete;