COM

Graph1:  TGraph;

procedure TForm2.GetProperty(dispobj: IDispatch; PropertyName: WideString;
                                var retvalue: Variant; Sender: TObject);
var hr: HRESULT;
    DispId: integer;
    value: Variant;
    params: TDispParams;
begin
  hr:=dispobj.GetIDsOfNames(GUID_NULL,@PropertyName, 1, LOCALE_SYSTEM_DEFAULT, @DispId);
  Label1.Caption:=inttostr(DispId);
  hr:=dispobj.Invoke(DispId,GUID_NULL,LOCALE_SYSTEM_DEFAULT,DISPATCH_PROPERTYGET,
                  Params,@Value,nil,nil);
  Retvalue:=Value;
  Label2.Caption:=inttostr(value);
end;

procedure TForm2.SetProperty(dispobj: IDispatch; PropertyName: WideString; Value: OLEVariant;
                                Sender: TObject);
var 
    hr: HRESULT;
    DispId: integer;
    params: TDispParams;
begin
   hr:=dispobj.GetIDsOfNames(GUID_NULL,@PropertyName,1, LOCALE_SYSTEM_DEFAULT, @DispId);
  Label1.Caption:=inttostr(DispId);
  params.rgvarg:=@Value;
  params.rgdispidNamedArgs:=@DispIDArgs;
  params.cArgs:=1;
  params.cNamedArgs:=1;
  hr:=dispobj.Invoke(DispId,GUID_NULL,LOCALE_SYSTEM_DEFAULT,
                  DISPATCH_PROPERTYPUT,Params,nil,nil,nil);
 end;

GetProperty(Graph1.GraphAxes, 'Color', retvalue, Sender);

SetProperty(Graph1.GraphAxes, 'Color',value,Sender);

if (ptr != 0) {
    *ptr = something;
    *ptr->AddRef ();
}

1. error C2259: cannot instantiate abstract class due to following members: unsigned long __stdcall IUnknown::AddRef(void)
   As the compiler said, you cannot instantiate this class in any way, because it misses something; if you write the code of that class the solution is obvious: implement unsigned long __stdcall IDgnWords::AddRef(void) and this will fix you problem
2. by writing IDgnWords* words; you have allocated only a pointer to that class, but you should initialize it with new IDgnWords() before use it. If you don't do it, the pointer hold a random address and trying to use it generates a memory protection faultCComPtr<IDgnWords> words; declares a smart-pointer to the IDgnWords class, then all that I said about IDgnWords* words; is still valid, and this is the reason of your crash. CComPtr simply wraps a IDgnWords* and calls the Release() method for you when the variable goes out of scope