Pass CustomerID to CustomerDeposit on click of custom button?

I am trying to add a button to the Sales Order form. This button should be accessible when VIEWING the Sales Order. Upon clicking the button, I would like the user to transfer to the Customer Deposit Page, ideally passing the Customer ID.

I have created a custom form for our Sales Order.

I have created the following javascript file, and uploaded it to the File Manager/Suite Scripts.

// Custom Code
// Add Customer Deposit Button to Sales Order/Customer
function myBeforeLoadFunc(type,form)
{
if (type == 'view')
{
var url = nlapiResolveURL('TASKLINK','EDIT_TRAN_CUSTDEP');
alert(url);
form.addButton("custpage_customerdepositbtn","Customer Deposit","document.location='"+url+"'");