RR AmountString(amount; curr; format) -> line

line      string (255)  returns the amount in words. It is empty when an
                                error occured.

amount  real              contains the number to convert to words. This
                                 number can be very large but is limited by the
                                 data used for the text and the maximum length set
                                 for the result string. But for each currency the
                                 maximum number is at least 999,999,999,999.
                                 The decimal digits are truncated to the number of
                                 digits (0, 2 or 3) needed for the specified
                                 currency.

curr      string (4)      indicates to which currency you want to convert.
                                 These are (based on) ISO 4217 currency codes.
                                 For multi-lingual countries a fourth character
                                 indicates the language.
                                 The currency codes which are supported are
                                 listed in the next chapter.

format  integer          specifys the format of the output string. See
                                 below for a list of supported formats.

With all formats you need to specify the currency, even with the plain format, in order to specify the language to use. When using the plain format the maximum number of digits after the decimal point is six, and not limited by the number normally used with the specified currency.
You won't notice much difference between formats 1, 2 and 3 when working with a currency which does not have minor units (i.e. Italian Lire and Portuguese Escudo).

Formats:
# name:    description:
0 plain    only words, no currency
           (twenty-three point nine two)
1 short    full with currency and number of units
           (twenty-three U.S. Dollars and 92 cents)
2 long     full with currenct and units string
           (twenty-three U.S. Dollars and ninety two cents)
3 official official with currency
           (twenty-three and 92/100 U.S. Dollars)

Examples:
  C_REAL($value)
  C_STRING (4; $currency)
  C_STRING (255; $result)
  C_INTEGER ($format)

  value := 1234.56
  currency := "USD"
  format := 1

  result := RR AmountString ($value; $currency; $format)

  ALERT ($result)