Insert code to a field

Hello,

I want to insert a javascript code ('onKeyUp' function) to address zip code field,
but following code does not work (cannot insert address field when editing form).
FYI, javasctipt code is inserted correctly to header section.

Any suggestions?

from common.php

// want to insert this function:  onKeyUp="AjaxZip3.zip2addr(this,'','input_6.4','input_6.3');"
$onKeyUp = sprintf("onKeyUp=\"AjaxZip3.zip2addr(this,'','input_%d.4','input_%d.3');\"", $id, $id);
$zip = sprintf("<span class='ginput_{$zip_location}$class_suffix' id='" . $field_id . "_5_container'><input type='text' name='input_%d.5' id='%s_5' value='%s' $tabindex %s $onKeyUp/><label for='%s_5' id='" . $field_id . "_5_label'>" . apply_filters("gform_address_zip_{$form_id}", apply_filters("gform_address_zip", $zip_label, $form_id), $form_id) . "</label></span>", $id, $field_id, $zip_value, $disabled_text, $field_id);

Hi, Carl.

Can you tell me where to modify code for insert OnKeyUp function to zip code field on the front end form?

Thanks,
Isao