function tab_chain("IBAN1", ["IBAN2", "IBAN3"]) {
    // Move to next field if the current keystroke
    // fills the field. Move to the previous field
    // if the current keystroke empties the field.

    // Pasted data that is too long for the current
    // will be continued into the fields listed in
    // the next_fields array.

    var rest, prev, next, i;
    event.change = event.change.toUpperCase();
    rest = event.changeEx.toUpperCase();
    var merged = AFMergeChange(event);
    //console.println("Name: '" + event.target.name + "'");
    //console.println("Merged: '" + merged + "'");

    if (merged.length === event.target.charLimit) {
        //console.println("Limit: " + event.target.charLimit);
        i = 0;
        prev = event.target;
        next = getField(["IBAN2", "IBAN3"]);
        rest = rest.substr(event.change.length);
        while (next !== null && rest.length > 0) {
            //console.println("Rest: " + rest);
            merged = rest.substr(0, next.charLimit);
            rest = rest.substr(merged.length);
            next.value = merged;
            prev = next;
            next = getField(["IBAN2", "IBAN3"]);
        }
        // Update focus if previous pasted field is full.
        if (next !== null && merged.length === prev.charLimit) {
            next.setFocus();
        }
    }
    else if (merged.length === 0) {
        getField("IBAN1").setFocus();
    }
}