def METHOD_NAME(self, current_text):
    try:
        molarMass = float(toMolarMass(self.model.item(MODEL.MOLECULAR_FORMULA).text()))
        molarDensity = float(current_text)
        molarVolume = molarMass / molarDensity
        molarVolume = formatNumber(molarVolume, high=True)
        self.model.item(MODEL.MOLAR_VOLUME).setText(str(molarVolume))
        # be sure to store the new value in the model
        self.model.item(MODEL.MASS_DENSITY).setText(current_text)
    except (ArithmeticError, ValueError):
        self.model.item(MODEL.MOLAR_VOLUME).setText("")