stop 'back' message in plugin

[sfx09]

Hello!

I'm doing a plugin for NSIS with a several forms (!), which are changing by clicking on 'Next' or 'Back' buttons.
My plugin work via Page Custom at this steps-condition:

!insertmacro MUI_PAGE_WELCOME
Page Custom MyPlugShow
!insertmacro MULTIUSER_PAGE_INSTALLMODE

Also, I try to change 'Cancel' button to Skip-functionality. So, if I try to click on 'Skip' ('Cancel') button, after click on the 'Next' button - all work fine - plugin go to MULTIUSER_PAGE_INSTALLMODE. But, if I try to click on 'Skip', after click on the 'Back' button - plugin page go to MUI_PAGE_WELCOME.

Please help me fix this.

Catching 'Skip' from plugin CurrentParentProc (Delphi):

PHP Code:

  if (uMsg = WM_COMMAND) then
  begin
    //esc or skip button
    if (LOWORD(wParam) = 2) and (HIWORD(wParam) = BN_CLICKED) then
    begin
      //ShowMessage('here click skip and skip on ESC!!!');
      bStopPlugin := TRUE;
      bSkipActivation := TRUE;
    end;
//...
  end; 


Boolean bStopPlugin - it is a "flag" for translate messages:

PHP Code:

  while bStopPlugin = FALSE do
  begin
    GetMessage(Msg, 0, 0, 0);
    if (not IsDialogMessage(PluginDialogFirstForm.Handle, Msg)) and (not IsDialogMessage(g_hwndParent, Msg))  then
    begin
      TranslateMessage(Msg);
      DispatchMessage(Msg);
    end;
  end; 


After, bSkipActivation - it is flag for skip. Also, I'm tried push 'next' in this statement, but - no luck.

PHP Code:

    if bSkipActivation = TRUE then
    begin
      //NSIS_PushString_Ansi('next');
      SetWindowLongPtr(g_hwndParent, SizeOf(LRESULT), Longint(parentOriginalWndproc));
      Exit;
    end; 


Sorry for my English. Help me, please.