Problem With Flicker

Okay, I need some help with this question: how do you get rid of that annoying flicker in brickfilms?? I try to only film at night and during the day I cover up the windows with blankets and I close the blinds but nothing seems to work! I use a Canon Rebel T3 and I have all the settings that I know about on manual so um... does anyone have a solution to my problem?