Advanced custom fields add functionality

Dear WordPress community,

I am using a WordPress plugin which is called “Advanced Custom fields” and I am very happy with its ease of use and functionalities.

What I am looking forward to achieve is to add a specific hook or functionality to one of my fields to open a popup field once clicked.

The code I have created and that I would like to run for the popup would be the following:

<script language="javascript" type="text/javascript">
    function popup(url)
    {
     var width  = 480;
     var height = 500;
     var left   = (screen.width  - width)/2;
     var top    = (screen.height - height)/2;
     var params = 'width='+width+', height='+height;
     params += ', top='+top+', left='+left;
     params += ', directories=no';
     params += ', location=no';
     params += ', menubar=no';
     params += ', resizable=no';
     params += ', scrollbars=no';
     params += ', status=no';
     params += ', toolbar=no';
     newwin=window.open(url,'windowname5', params);
     if (window.focus) {newwin.focus()}
     return false;
    }
    </script>

    <input type="text" name="field" id="field"onclick="javascript:popup('https://myurl', '200', '200', '510', '440');return false;">

The code of my field looks as follows:

<div id="acf-custom_field" class="field field-text"><p class="label"><label for="fields[field_5007b7f298fd6]">Custom field</label></p><input type="text" value="" id="fields[field_5007b7f298fd6]" class="text" name="fields[field_5007b7f298fd6]"></div>

Is there an easy way (for example by adding something in theme-functions) to add a on click event to this specific item?

Some expert advise would be highly appreciated.

Thank you very much,
Patrick