ConvertASCIIToANSI FOB example

Yes, I used that one too but had problems with import. Will check this one out. Thx.

Ps.
How can you add your own characters. Is there a howto?

That number belongs to a localization, so it's not part of every standard database. Could you tell us which localization you are working with?

Yes, the sample codeunit is merely a copy (with some empty additional functions) of the localized standard NAV 4.0 (SP1) Codeunit 11501 (VersionList=NAVDACH4.00.01).
There is another (earlier) version of this codeunit in NAV 4.0 (VersionList=NAVDACH4.00) which is much more transparent and easier to extend, since it uses integer codes instead of letter symbols:

OBJECT Codeunit 11501 GeneralMgt
{
  OBJECT-PROPERTIES
  {
    Date=23.09.04;
    Time=12:00:00;
    Version List=NAVDACH4.00;
  }
  PROPERTIES
  {
    OnRun=BEGIN
          END;

  }
  CODE
  {
    VAR
      Text001@1150000 : TextConst 'DEU=Der Ordnername muss auf einen Schr„gstrich enden, d. h. %1.;ENU=The folder name must end with a slash character, i.e. %1.';

    PROCEDURE CheckFolderName@2(VAR _Input@1150000 : Text[250]) _Output@1150001 : Text[250];
    BEGIN
      // Check for ending slash of folder name
      IF _Input = '' THEN
        EXIT;

      IF NOT (COPYSTR(_Input,STRLEN(_Input)) IN ['\','/']) THEN
        MESSAGE(Text001,'c:\data\');
    END;

    PROCEDURE Ansi2Ascii@10(_String@1150001 : Text[250]) _Output@1150000 : Text[250];
    VAR
      i@1150003 : Integer;
      Z@1150002 : Char;
    BEGIN
      // Converts from ANSI to ASCII

      FOR i := 1 TO STRLEN(_String) DO BEGIN

        Z := _String[i];

        CASE Z OF
          // Convert special chars in ASCII
          228: Z := 132; // „   ANSI=Alt0228, ASCII=Alt132
          196: Z := 142; // Ž
          226: Z := 131; // ƒ
          224: Z := 133; // …
          225: Z := 160; //  
          229: Z := 134; // †
          197: Z := 143; // 
          230: Z := 145; // ‘
          198: Z := 146; // ’

          199: Z := 128; // €
          231: Z := 135; // ‡

          233: Z := 130; // ‚
          234: Z := 136; // ˆ
          235: Z := 137; // ‰
          232: Z := 138; // Š
          201: Z := 144; // 

          239: Z := 139; // ‹
          238: Z := 140; // Œ
          236: Z := 141; // 
          237: Z := 161; // ¡

          246: Z := 148; // ”
          214: Z := 153; // ™
          244: Z := 147; // “
          242: Z := 149; // •
          243: Z := 162; // ¢

          252: Z := 129; // 
          220: Z := 154; // š
          251: Z := 150; // –
          249: Z := 151; // —
          250: Z := 163; // £

          241: Z := 164; // ¤
          165: Z := 209; // ¥
          255: Z := 152; // ˜
          163: Z := 156; // œ
          248: Z := 157; // ›
        END;

        _String[i] := Z;
      END;

      EXIT(_String);
    END;

    PROCEDURE Ascii2Ansi@1150001(_String@1150001 : Text[1024]) @1150000 : Text[1024];
    VAR
      NoProcessed@1150002 : Integer;
      i@1150003 : Integer;
      Z@1150004 : Char;
    BEGIN
      // Converts from ASCII to ANSI

      FOR i := 1 TO STRLEN(_String) DO BEGIN

        Z := _String[i];

        CASE Z OF

          // Convert special chars in ANSI
          132: Z := 228; // „  ASCII=Alt132, ANSI = Alt0228
          142: Z := 196; // Ž
          131: Z := 226; // ƒ
          133: Z := 224; // …
          160: Z := 225; //  
          134: Z := 229; // †
          143: Z := 197; // 
          145: Z := 230; // ‘
          146: Z := 198; // ’

          128: Z := 199; // €
          135: Z := 231; // ‡

          130: Z := 233; // ‚
          136: Z := 234; // ˆ
          137: Z := 235; // ‰
          138: Z := 232; // Š
          144: Z := 201; // 

          139: Z := 239; // ‹
          140: Z := 238; // Œ
          141: Z := 236; // 
          161: Z := 237; // ¡

          148: Z := 246; // ”
          153: Z := 214; // ™
          147: Z := 244; // “
          149: Z := 242; // •
          162: Z := 243; // ¢

          129: Z := 252; // 
          154: Z := 220; // š
          150: Z := 251; // –
          151: Z := 249; // —
          163: Z := 250; // £

          164: Z := 241; // ¤
          165: Z := 209; // ¥
          152: Z := 255; // ˜
          156: Z := 163; // œ
          157: Z := 248; // ›
        END;

          _String[i] := Z;
      END;

      EXIT(_String);
    END;

    BEGIN
    END.
  }
}

Note, that the letter signs (in the comments) are displayed correctly, if you import the object (may be with different object ID) into NAV.