Set Destination When Creating Automated Button

I've been trying to use the setFocus method dynamically by assigning it to a "setAction." I placed in my new button and each time I try it fails to work. 

 Below is where I want setFocus, a new button would be able to navigate to a reference button called (i.e. "BACK-A1, A2, A3, etc.")

Is focus only used once throughout the document? I would love to assign each button to its own unique "focus point."

 function CreateField(){

     var newButton = this.addField("newButton" + aCount, "button", this.pageNum, [0, 20, 80, 0]);

     aCount++

     newButton.buttonSetCaption("FINDING" + " A-" + aCount);

    ** Below is the issue **

     newButton.setAction("MouseUp", "this.getField("BACK-A" + aCount).setFocus();")"

     return newButton;

}

CreateField();