VB не ми е интересен. Ето на Python:

roman_map = {'':0, 'I':1, 'IV':4, 'V':5, 'IX':9, 'X':10, 'XL':40, 'L':50, 

                'XC':90, 'C':100, 'CD':400, 'D':500, 'CM':900, 'M':1000}



romans_sorted = [r for (r,a) in sorted( roman_map.items(), 

                                        cmp = lambda (r1,a1),(r2,a2): a2-a1 )]



def arabic (r):

    if len(r) <= 1:

        return roman_map[r]

    k = (1,2)[ roman_map.has_key( r[:2] )]

    return roman_map[ r[:k] ] + arabic( r[k:] )



def roman( a, s=""):

    for r in romans_sorted:

        rest = a - roman_map[r]

        if  rest >=0 and a>0:

            return roman(rest, s + r)

    return s

    

                

assert roman ( 1888 ) == 'MDCCCLXXXVIII'

assert arabic ( roman ( 1280 ) ) == 1280 #citizens



assert roman ( 1999 )  == 'MCMXCIX'

assert arabic ( roman ( 1999 ) ) == 1999