function checkNumber(object_value) {
    /* Returns true if value is a number or is NULL
       otherwise returns false */

  if (object_value.length == 0)
      return true;

    /* Returns true if value is a number defined as
       having an optional leading + or -.
       having at most 1 decimal point.
       otherwise containing only the characters 0-9. */
	var start_format = " .+-0123456789";
	var number_format = " .0123456789";
	var check_char;
	var decimal = false;
	var trailing_blank = false;
	var digits = false;

    /* The first character can be + - .  blank or a digit. */
	check_char = start_format.indexOf(object_value.charAt(0));
    /* Was it a decimal? */
	if (check_char == 1)
	  decimal = true;
	else if (check_char < 1)
		return false;
        
	/* Remaining characters can be only . or a digit, but only one decimal. */
	for (var i = 1; i < object_value.length; i++)	{
		check_char = number_format.indexOf(object_value.charAt(i));

		if (check_char < 0)
			return false;
		else if (check_char == 1)	{
			if (decimal)		/* Second decimal. */
				return false;
			else
				decimal = true;

		}	else if (check_char == 0)	{

			if (decimal || digits)	
				trailing_blank = true;
        /* ignore leading blanks */

		} else if (trailing_blank)
			return false;

		else
			digits = true;
	}	
    /* All tests passed, so... */
	return true
}