From Select To Update

I have a sales table that has a customer_number, salesman_number and sales data (like item, quantity, etc), there is a customer table that has the customer_number, name, address, etc. and salesman_number, with the passign of time salesmen come and go and the customer service department is in charge of modifying the customer table and assign the new salesman number to them. All the previous sales have to be reasigned to this new salesman even though it wasnt him the one that sold the items (I know, I know, thats the way the company requieres it, this is an old system). Now to my question:

I have this select query that gives me the rows from table sales that have to be modified:

SELECT C.sales_rep,S.salesrep,S.*
FROMSALES AS S
INNER JOIN customer AS C
ONC.Active_Flag = 'A' AND
C.sales_rep != 'XXXX' AND
C.site_code = S.site_code AND
C.cust_no = S.cust_noAND
C.cust_sffx = S.cust_sffxAND
C.division = S.divisionAND
C.sales_rep != S.salesrep
WHERES.month = 2AND
S.year = 2005
ORDER BYC.sales_rep

I just want to know if my approach to convert this query from an update to a select is ok:

UPDATE SALES AS S
SET S.salesrep = C.sales_rep
INNER JOIN customer AS C
ONC.Active_Flag = 'A' AND
C.sales_rep != 'XXXX' AND
C.site_code = S.site_code AND
C.cust_no = S.cust_noAND
C.cust_sffx = S.cust_sffxAND
C.division = S.divisionAND
C.sales_rep != S.salesrep
WHERES.month = 1AND
S.year = 2004

Thanks for your help

Luis Torres