please can someone help

i have two tables with info in
is it possible to update a record in one table with a record from anoher table

this is the code to do it in MS Access

UPDATE tblPromo, tblCurrentUser
SET tblPromo.PromoOperator = [UserName]
WHERE (((tblPromo.PromoOperator) Is Null));

i want to get the username from the tblcurrentuser and put it in Promooperator in tblPromo where PromoOperator is null

hope someone can undesrtand me and help
thanks