应用软件中如何实现多币种自动换算

mlwbpj字段列表：
id        int4         32 键号            textedit          
hbdh      varchar      50 贷币代号          textedit          
hbmc      varchar      20 货币名称          textedit          
jzhl      numeric      18 记账汇率(每100外币)  textedit        n4
sfsh      bool          0 是否审核          checkedit         
shry      varchar      20 审核人员          textedit          
rq        date          0 日期            dateedit  yyyy-MM-dd

CREATE OR REPLACE FUNCTION public.x9_bbje(
  ywrq date,
  wbmc character varying,
  wbsl numeric)
    RETURNS numeric
    LANGUAGE 'plpgsql'
    COST 100
    VOLATILE PARALLEL UNSAFE
AS $BODY$
   -- Description:  本币金额
DECLARE
   bbje decimal(16,4);
   pjrq DATE;
BEGIN
  bbje:=0;
  IF $2 = '人民币(RMB)' OR $2 = '' THEN
    BEGIN
       bbje:=$3;
    END;
  ELSE
    BEGIN
      IF $3 IS NULL THEN $3 = 0;END IF;
      SELECT max(rq) INTO pjrq FROM mlwbpj WHERE rq <= $1;
      SELECT (jzhl * $3) / 100 INTO bbje FROM mlwbpj WHERE rq = pjrq AND hbmc = $2 ;
    END;
  END IF ;
  RETURN bbje;
END;
$BODY$;

CREATE OR REPLACE FUNCTION public.x9_wbje(
  wbmc character varying,
  bbsl numeric)
    RETURNS numeric
    LANGUAGE 'plpgsql'
    COST 100
    VOLATILE PARALLEL UNSAFE
AS $BODY$
   -- complete date:2022-09-18-- Description: 外币金额 
DECLARE
    ssmsg text;ssdet text;sstname text;sshint text;ssctt text; --错误处理
  wbje decimal(16,4);
  pjrq DATE;
BEGIN
  wbje:=0;
  IF $1 = '人民币(RMB)' OR $1 = '' THEN
     wbje:=0;
  ELSE
    IF $2 IS NULL THEN 
         wbje = 0;
      END IF ;
    SELECT max(rq) INTO pjrq FROM mlwbpj WHERE hbmc = $1;
    SELECT ($2 * 100 / jzhl) INTO wbje FROM mlwbpj WHERE hbmc = $1 AND rq = pjrq;
  END IF ;
  RETURN wbje;
   EXCEPTION WHEN others THEN
      GET stacked DIAGNOSTICS ssmsg = MESSAGE_TEXT,ssdet = pg_exception_detail,
         sstname = TABLE_NAME, sshint = pg_exception_hint, ssctt = pg_exception_context;
      CALL x9_jlproc(ssmsg, ssdet, sstname, sshint, ssctt);
      RETURN 0;
END;
$BODY$;