void NegateSign()
{
Word.Signs sign = mWord.Sign;
mWord.InvertSign();
mLastRenderedMagnitude = mWord.MagnitudeLongValue;
mLastRenderedSign = mWord.Sign;
mSignButton.Text = "" + mWord.Sign.ToChar();
var oldValue = new Word(mWord.Magnitude, sign);
var newValue = new Word(mWord.Magnitude, mWord.Sign);
OnValueChanged(new WordEditorValueChangedEventArgs(oldValue, newValue));
}