place picture to the button?

Hi

I tryed to place picture to a button with this code. It works great in standard and pro but not in reader?

It seems to work in reader, dialogbox appears, I chose a picture but - no visible picture after all?

Can anyone help?

var z=this.getField("resumeField");
z.browseForFileToSubmit();
var f=this.getField("myButton");
f.buttonImportIcon(z.value);
f.display=display.visible;