linked pdf fields -- backspacing code?

Hi, I have two fields linked together in a pdf, so that the text flows from one line to the next... using this code:

// Move to next field when this one is full

var t=this.getField ("strongpoints1");

if (event.fieldFull) {

    getField("strongpoints2").setFocus();

}

Can anyone direct me to a coding solution that allows me to backspace from the second field back through the first field? Right now, I have to click each field individually to backspace the content on that line. But I would like it to automatically backspace up through the previous line.

Thank you!