Returning more than one result set from a stored procedure

CREATE PROCEDURE procBillingSummaryCastingDollars(
			@startDate Varchar(10),@endDate Varchar(10))  AS

DECLARE @invoice_id varchar(11);


DECLARE invoice_cursor CURSOR FOR 
SELECT invoice_id
FROM receivable_dist rd 
WHERE rd.POSTING_DATE BETWEEN @startDate AND @endDate 
AND (rd.GL_ACCOUNT_ID like '%3000%' OR rd.GL_ACCOUNT_ID like '%3101%') 
order by invoice_id

OPEN invoice_cursor

FETCH NEXT FROM invoice_cursor 
INTO @invoice_id

WHILE @@FETCH_STATUS = 0
BEGIN
   -- Declare an inner cursor based   
   -- on invoice_id from the outer cursor.
   IF charindex('C',@invoice_id) = 0 AND charindex('M',@invoice_id) = 0
   BEGIN
   	   SELECT ss.metal_code, ss.equip_code, ss.core,
	   CASE r.status WHEN 'X' THEN rl.amount*-1 ELSE rl.amount END as CastingDollars
	   FROM receivable r
	   INNER JOIN receivable_line rl ON r.invoice_id = rl.invoice_id
	   INNER JOIN cust_order_line  cl ON cl.cust_order_id = rl.cust_order_id
	   INNER JOIN salesum_partid ss ON ss.partid = cl.part_id
	   WHERE rl.invoice_id = @invoice_id
   END
   ELSE
   BEGIN
	   SELECT ss.metal_code, ss.equip_code, ss.core, 
	   CASE r.status WHEN 'X' THEN rl.amount*-1 ELSE rl.amount END as CastingDollars
	   FROM receivable r
	   INNER JOIN receivable_line rl ON r.invoice_id = rl.invoice_id
	   INNER JOIN salesum_partid ss 
		ON substring(ltrim(rl.reference),1,(patindex('%-_-____%',ltrim(rl.reference))+6)) = ss.partid
	   WHERE r.invoice_id = @invoice_id
   END

   FETCH NEXT FROM invoice_cursor 
   INTO @invoice_id
END

CLOSE invoice_cursor
DEALLOCATE invoice_cursor
GO