🚀 go-pugleaf

I've posted this question to borland.public.cppbuilder.students but
the answer I got is insufficient. I think
borland.public.cppbuilder.nativeapi
is the right place to ask.

I have an application with 2 forms. (Form1 and Form2)
Form1 consists of 3 ListViews all in vsReport mode.
The OwnerData properties are set to true for all of them.

If I click a button on Form1, Form2 is displayed and executes
a function automatically. After execution of this function Form2 should be
automatically closed.
The minimal code is below:

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    Form2->ShowModal();
}

void f()
{
    ...
}

void __fastcall TForm2::FormActivate(TObject *Sender)
{
    f();
    Caption = "Post message is executing";
    PostMessage((HWND)(Handle),WM_CLOSE,0,0);
    Caption = "Post message executed";
}

I was told to use PostMessage() instead of Close() in a FormActivate()
function a long time ago.
Another program(very similar in implementation) of mine works well with this
PostMessage() function
but this program doesn't. I don't know why.
The problem is, PostMessage() function doesn't close the Form2 sometimes
.(aprox. 5%)
f() function is executed, then (sometimes) Form2 remains forever unless I
move the mouse (even 1 pixel),
click the mouse button or press a key.Changing mouse cursor position with
Mouse->CursorPos = TPoint(Mouse->CursorPos.x, Mouse->CursorPos.y - 10);
also closes Form2.

If Form2 remains forever, I can see the "Post message executed" string as
caption, and this implies that PostMessage is executed..
So, how can I close Form2?. What are the suggestions?