function DetectBT: PChar; stdcall; external 'foobar.dll';
//type
//  TDetectBT = function: PChar; stdcall;


procedure TForm1.Button1Click(Sender: TObject);
//var
//  hDll: cardinal;
//  xDetectBT: TDetectBT;

begin
//  hDll := LoadLibrary('foobar.dll');
//  if hDll <> 0 then begin
//    @xDetectBT := GetProcAddress(hDll, 'DetectBT');
//    if Assigned(@xDetectBT) then
      Caption := {x}DetectBT;
//    FreeLibrary(hDll);
//  end;
end;





library foobar;

uses
  SysUtils,
  Windows,
  Registry,
  Classes;

{$R *.res}

function DetectBT: PChar; stdcall;
var
  xReg: TRegistry;
  sTemp: PChar;

begin
  sTemp := '';
  xReg := TRegistry.Create;
  xReg.RootKey := HKEY_CURRENT_USER;
  xReg.OpenKey('Control Panel\Current', False);
  sTemp := PChar(xReg.ReadString('Color Schemes'));
  xReg.CloseKey;
  FreeAndNil(xReg);
  Result := sTemp;
end;

exports
  DetectBT;

begin
end.