Convert number to string

Hi,

I don’t have any idea how can I use postgres function to convert series  of number (currency) to my own string.

My string         : F G H I J K L M N  as the replacement for number : 1 2 3 4 5 6 7 8 9

Dozens = O

Hundreds = P

Thousands = C

Ten thousands = B

So…

200 = GP

2000 = GC

1150 = FFJO

30000 = HB

Any idea ?

Thanks In advance