Convertir une valeur Hexadecimale en integer

function StrToHex(s : string) : LongWord;
var
b : Byte;
c : Char;
begin
Result := 0;
s := UpperCase(s);
for b := 1 to Length(s) do
begin
Result := Result * 16;
c := s[b];
case c of
'0'..'9': Inc(Result, ord(c) - ord('0'));
'A'..'F': Inc(Result, ord(c) - ord('A')+10);
else raise EConvertError.Create('Keine Hexadezimal-Zahl');
end;
end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
ShowMessage(IntToStr(StrToHex('AAF1'))); // > 43761
end;