putting code into a form

[geewizz]

Username: Geewizz
URL: www.innovation-nation.co.uk

Hi I wonder id anybody can help me with the following:

I am trying to hook up a form to a google map and have been told to add id="PostCode" to my <input type="text"> tag, and add the following to my <form> tag:

onsubmit="closestMarkerSearch(map, markers, 10, document.getElementById('PostCode').value); return false"

How do I do this

Please help

Geewizz