Concatenate fields and use the Alias field to link another field in another table

I have two tables that I would like to link together for making labels.  I would like to link the tables together to get my results.   The issue lies when I inner join the tables.  table a has two fields and table b has one field that I need to link together to get my results.  I was able to get the alias to link the tables together, but I get stuck on how to link an alias to another table in the same query.

Here is the tables and my query
Work_Order
Base_ID       Lot_ID   Part_ID        Printed_Date
WO-00009    1           112A7000    12/31/2012

Trace
Part_ID         AProperty_1      SN
112A7000     WO-00009/1     SN1223

I would like the results to be
Part_ID          SN              Printed_Date
112A7000     SN1223      12/31/2012

I think my issue is with the Alias . .

SELECT WORK_ORDER.BASE_ID, WORK_ORDER.LOT_ID, WORK_ORDER.PART_ID, [WORK_ORDER].[BASE_ID]+ '/' + [WORK_ORDER].[LOT_ID] AS WO
FROM WORK_ORDER
INNER JOIN TRACE ON WORK_ORDER.PART_ID = TRACE.PART_ID AND WO = TRACE.APROPERTY_1
WHERE WORK_ORDER.PRINTED_DATE > 12/31/12

Thanks so much!!  Happy New Year!!