function FindCert(const Store, FileName: string): Integer;
var
  CertFile: file;
  hStore: HCERTSTORE;
  PKCS7Length: Integer;
  Buf: Pointer;
  pFindCon, pCertCon: PCCERT_CONTEXT;
  leng: Integer;
begin
  Result := -1;
  try
    try
      AssignFile(CertFile, FileName);
      ReSet(CertFile, 1);
      PKCS7Length := FileSize(CertFile);
      Buf := AllocMem(PKCS7Length);
      if not Assigned(Buf) then
        Abort;
      blockread(CertFile, Buf^, PKCS7Length, leng);
      if PKCS7Length <> leng then
        RaiseLastOSError;
      hStore := CertOpenSystemStore(0, pChar(Store));
      pCertCon := CertCreateCertificateContext(X509_ASN_ENCODING or
        PKCS_7_ASN_ENCODING, Buf, PKCS7Length);
      if not Assigned(pCertCon) then
        RaiseLastOSError;
      pFindCon := CertFindCertificateInStore(hStore, X509_ASN_ENCODING or
        PKCS_7_ASN_ENCODING, 0, CERT_FIND_EXISTING, pCertCon, nil);
      if Assigned(pFindCon) then
      begin
        CertFreeCertificateContext(pFindCon);
        Result := 0;
        Exit;
      end
        else RaiseLastOSError;
    finally
      if Assigned(Buf)
        then FreeMem(Buf);
      CloseFile(CertFile);
      if Assigned(pCertCon)
        then CertFreeCertificateContext(pCertCon);
      CertCloseStore(hStore, 0);
    end;
  except
    on E: EOSError do
      Result := E.ErrorCode;
    on E: EInOutError do
      Result := E.ErrorCode;
  end;
end;

CertGetCertificateContextProperty(pCertCont,param, PByte(buffer), DataLen)

c.cbData:=DataLen;
c.pbData:=buffer;

  CertCont:=CertFindCertificateInStore(hCStore,X509_ASN_ENCODING or PKCS_7_ASN_ENCODING{enc},0{flag},CERT_FIND_HASH,@c,nil);
  res:=GetLastError();
  writeln(stderr,inttohex(res,8));
  // CRYPT_E_NOT_FOUND $80092004
  if res=$80092004 then CertCont:=nil;

CertOpenSystemStore(0,'MY');
CertOpenStore(CERT_STORE_PROV_SYSTEM_A,0,0,CERT_STORE_OPEN_EXISTING_FLAG or CERT_STORE_READONLY_FLAG or CERT_SYSTEM_STORE_LOCAL_MACHINE,Pchar('MY'));

hStore:=CertOpenStore(CERT_STORE_PROV_SYSTEM_W,0,0,CERT_STORE_OPEN_EXISTING_FLAG or CERT_SYSTEM_STORE_LOCAL_MACHINE,PWidechar('MY'));