REM Used the following as official standard:
      REM  http://www.cnb.cz/cs/platebni_styk/iban/download/EBS204.pdf

      REM Pairs of ISO 3166 country code & expected IBAN length for this country
      COULEN$="AL28 AD24 AT20 AZ28 BE16 BH22 BA20 BR29 BG22 CR21 HR21 CY28 CZ24 DK18 DO28 EE20 "+\
      \       "FO18 FI18 FR27 GE22 DE22 GI23 GR27 GL18 GT28 HU28 IS26 IE22 IL23 IT27 KZ20 KW30 "+\
      \       "LV21 LB28 LI21 LT20 LU20 MK19 MT31 MR27 MU30 MC27 MD24 ME22 NL18 NO15 PK24 PS29 "+\
      \       "PL28 PT25 RO24 SM27 SA24 RS22 SK24 SI19 ES24 SE24 CH21 TN24 TR26 AE23 GB22 VG24"

      PROCIBANcheck("GB82 WEST 1234 5698 7654 32"):REM Paper IBAN notation (with the spaces)
      PROCIBANcheck("GB82WEST12345698765432")     :REM Digital IBAN notation (without the spaces)
      PROCIBANcheck("gb82 west 1234 5698 7654 32")
      PROCIBANcheck("GB82 TEST 1234 5698 7654 32")
      PROCIBANcheck("GR16 0110 1250 0000 0001 2300 695")
      PROCIBANcheck("GB29 NWBK 6016 1331 9268 19")
      PROCIBANcheck("SA03 8000 0000 6080 1016 7519")
      PROCIBANcheck("CH93 0076 2011 6238 5295 7")
      PROCIBANcheck("IL62 0108 0000 0009 9999 999")
      PROCIBANcheck("IL62-0108-0000-0009-9999-999")
      PROCIBANcheck("US12 3456 7890 0987 6543 210")
      PROCIBANcheck("GR16 0110 1250 0000 0001 2300 695X")
      END

      DEF PROCIBANcheck(iban$)
      LOCAL err$,i%,match%,explen%,digiban$,tmpiban$,bignum$,c%,kk%

      REM Search for country code and fetch expected length
      i%=1:explen%=0
      WHILE explen%=0 AND i%<LENCOULEN$
        IF LEFT$(iban$,2)=MID$(COULEN$,i%,2) explen%=VALMID$(COULEN$,i%+2,2)
        i%+=5
      ENDWHILE
      match%=explen%>0

      REM Continue if country code found
      IF match% THEN
        REM Remove space = convert to digital IBAN
        digiban$=""
        FOR i%=1TOLENiban$
          IF MID$(iban$,i%,1)>" " digiban$+=MID$(iban$,i%,1)
        NEXT
        REM Compare length with expected length
        match%=explen%=LENdigiban$

        REM Continue if length is correct
        IF match% THEN
          REM Create temporary string with country code appended
          tmpiban$=MID$(digiban$,5)+MID$(digiban$,1,2)
          REM Make big number, replacing letters by numbers using next conversion table: A=10 ... Z=35
          bignum$=""
          FOR i%=1TOLENtmpiban$
            c%=ASCMID$(tmpiban$,i%,1)
            IF c%>57 bignum$+=STR$(c%-55) ELSE bignum$+=STR$(c%-48)
          NEXT
          REM MOD 97 on bignum$+"00" and subtract result from 98 to obtain control number
          kk%=98-FNmod97(bignum$+"00")
          REM Compare with control number in IBAN
          match%=VALMID$(iban$,3,2)=kk%

          REM Continue if control number matches
          IF match% THEN
            REM Append kk% to bignum$ and determine if MOD 97 results in 1
            match%=FNmod97(bignum$+RIGHT$("0"+STR$kk%,2))=1

            REM Continue if MOD 97
            IF match% THEN
              REM Was last test
            ELSE
              err$="result from modulo 97"
            ENDIF
          ELSE
            err$="check digits, should be: "+STR$kk%
          ENDIF
        ELSE
          err$="code length, expected length: "+STR$explen%
        ENDIF
      ELSE
        err$="country code: "+LEFT$(iban$,2)
      ENDIF

      IF match% PRINT "  "; ELSE PRINT "in";:err$="***error!*** invalid "+err$
      PRINT "valid IBAN: ";iban$TAB(50)err$
      ENDPROC

      DEF FNmod97(num$)
      LOCAL mod$
      mod$=LEFT$(num$,2)
      num$=MID$(num$,3)
      WHILE num$>""
        mod$=RIGHT$("0"+STR$(VAL(mod$+LEFT$(num$,7))MOD97),2)
        num$=MID$(num$,8)
      ENDWHILE
      =VALmod$