def ok(self):
        """
        Returns True if OK to use, else False
        """
        try:
            v = int(self._value)
            chunk = self.mfac.value()
            if v < self.imin or v > self.imax or (v % chunk != 0):
                return False
            else:
                return True
        except:
            return False
Returns True if OK to use, else False