How to set window position to locate it to the top of the screen on MFC?

How to set window position to locate it to the top of the screen on MFC?

I'm trying to set position of new dialog in MFC, what i do:
SetWindowPos(&this->wndTopMost, 0,0,0,0, SWP_NOSIZE);
in the InitDialog() of this window, but after execution, this window
appears on center of my screen... What am i doing wrong?