[newbie]StaticBox resize -> core dump

[Tomasz Sienkiewicz]

Hi, i have created form, that has panel on it and i put staticbox component onto panel. I want to do docking.

Now, i capture OnSize event inside FORM

Snippet:

void Form::OnSize(wxSizeEvent& event )
{
this -> Panel -> SetSize(this.GetSize());

this -> StaticBox -> SetSize( this-> Panel ->GetSize().GetWidth - 100 ,this-StaticBox->GetSize().GetHeight());  // 
}

if I leave this -> StaticBox -> SetSize( this-> Panel ->GetSize().GetWidth - 100 ,this-StaticBox->GetSize().GetHeight()) uncommented I will get core dump (linux) or illegal operation (win) at start of programm.
Am I missing something ? How to avoid it? What am i doing wrong?