Add Button field with script attached

I'm trying to programmatically add a button with some Javascript code. This button when click should go to a specific page. Simple right? For some reason I can't get it to work. I know it is something simple I'm missing but it just won't work. I'm not getting any error messages. The button is there but it doesn't execute the code.

Can someone please help?

Code:

var btn = this.addField("link","button",0, [140, 685, 470, 665]);
btn.setAction = ("MouseUp", "this.pageNum=7;");
btn.delay = true;
btn.highlight = "push";
btn.fillColor = color.transparent;
btn.delay = false;

Thanks,

scopley