Need Help With Calculating Total Row In Query

I quess it should be simple. But I couldn't find an answer or example in Access books and online.
I have an access 2000 database with a Accounts Receivable table. I am building a query that returns accounts what are 60 days past due and calculating total ballance of ONLY past 60 days accounts. I managed to write a code to display 60 days past due acounts, but when I use UNION query, it calculates total from entire Accounts Receivable table, but I need only total ballance of past due accounts.

Here is my SQL code

SELECT [Accounts Receivable].InvoiceID, [Accounts Receivable].[Patient Last Name], [Accounts Receivable].[Patient#], [Accounts Receivable].InvoiceDate, [Accounts Receivable].PaymentAmount
FROM [Accounts Receivable]
WHERE ((([Accounts Receivable].InvoiceDate)<Date()-60))
UNION SELECT 'TOTAL', "","","",Sum([Accounts Receivable].PaymentAmount)
FROM [Accounts Receivable];

I need my query to look like this.

InvoiceID Patient Last Name Invoice Date Payment Amount

23 Smith 05/01/2007 $100
25 Doe 04/03/2007 $200
Total - - $300

Please help.