Complex permanent background

[LEFT][FONT=Calibri][SIZE=3][COLOR=#000000]Hi,[/COLOR][/SIZE][/FONT]
[FONT=Calibri][SIZE=3][COLOR=#000000]I want to have an experiment in which a yellow rectangle appear constantly in the middle of a black screen, and some little stimulus are showing inside the rectangle at 4 different locations at a randomize order. Every time that a little stimuli appears, its counts as a trial and write the subject response. [/COLOR][/SIZE][/FONT]
[FONT=Calibri][SIZE=3][COLOR=#000000]Can I somehow define a permanent background of a big yellow rectangle inside the all black screen? I tried to make 4 stimulus of the rectangle with the little stimuli at 4 different locations. The problem is that the rectangle is disappearing when moving from trial to trial and I need it to stay. Is there a way to do this?[/COLOR][/SIZE][/FONT]
[FONT=Calibri][SIZE=3][COLOR=#000000] [/COLOR][/SIZE][/FONT]
[FONT=Calibri][SIZE=3][COLOR=#000000]Thank you,[/COLOR][/SIZE][/FONT]
[FONT=Calibri][SIZE=3][COLOR=#000000]Roy[/COLOR][/SIZE][/FONT][/LEFT]