Problems with maximize window

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C++

MFC

My dialog opens with initial size, dialog has a button, If I press it dialog must maximize, and if I press it again, window must assume initial size..
My code:

<pre>
void CDlgEstimateTime::OnBnClickedMaximize()
{
	if (m_bMinMax == false)
	{
		ShowWindow(SW_MAXIMIZE);
		m_bMinMax = true;
	}
	else
	{	
	    this->SetWindowPos(this, 0, 0, m_nWidthInitial, m_nHightInitial, SWP_NOREPOSITION | SWP_NOCOPYBITS | SWP_NOZORDER | SWP_SHOWWINDOW);
		CenterWindow();
		m_bMinMax = false;	
	}
}

the problem is that: IF I press button window maximizes, I press button again and window assumes initial size, but if I press again window doesn't maximizes but size are fixed

What I have tried:

I tried code that I've written..