A different showpoly question

[Omini]

I have

PHP Code:

with (findImg(4000)) {
        polygon = { 0, 0, screenwidth, 0, screenwidth, screenheight, 0, screenheight};
        alpha = 0.3;
        red = 0.9;
        green = 0.9;
        blue = 0.9;
        layer = 4;
      } 


I also tried

PHP Code:

with (findImg(4000)) {
        polygon = { 0, 0, screenwidth, 0, screenwidth, screenheight, 0, screenheight};
        this.alpha = 0.3;
        this.red = 0.9;
        this.green = 0.9;
        this.blue = 0.9;
        layer = 4;
      } 


But it doesnt appear to work... anything noticable that's causing the problem?