def at_most_3_in_row_ixcm(string):
    """
    True if IXCM do not occur more than 3 times in a row, False otherwise.

    PARAMETERS:
        string : str

    RETURNS: bool
    """
    ixcm = ("I", "X", "C", "M")
    
    current_letter = ""
    letter_count = 0

    for letter in string:
        if letter in ixcm:
            # Count sequential occurrences
            # If any of those counts reaches 4, returns False. True otherwise
            if letter != current_letter:
                current_letter = letter
                letter_count = 1
            else:
                letter_count += 1
                if letter_count > 3:
                    return False
        
        # If letter not one of IXCM, reset current_letter and count
        else:
            current_letter = ""
            letter_count = 0
    
    return True