Runwait() waits for the run to complete. What you do in the loop above is to run it 4 times. If the takeown program returns progress data to the console you could read the stdout stream, but as not many console programs do this there is just no way to estimate the overall runtime.
As a workaround create the progres control with the $PBS_MARQUEE flag set to indicate that something is happening, here's a piece of pseudo-code:
#include <SENDMESSAGE.AU3>
$c_Progress = GUICtrlCreateProgress(9, 35, 340, 17, $PBS_MARQUEE)
$h_Progress = GUICtrlGetHandle($c_Progress)
_SendMessage($h_Progress, $PBM_SETMARQUEE, True, 0)
RunWait('TAKEOWN /f ' & '"' & $Select0 & '"' & ' /r /d y', "", @SW_HIDE)
_SendMessage($h_Progress, $PBM_SETMARQUEE, False, 0)