I have an Outer Join that works in the query below

SELECT ItemT.itemName, nz(Sum(TransT.qty),0) AS SumOfqty, TransT.custID
FROM ItemT LEFT JOIN TransT ON ItemT.itemID = TransT.itemID
WHERE TransT.CustID=forms!CustomerF![CustomerCBO]
GROUP BY ItemT.itemName, TransT.custID;

I have a form that has a combo box CustomerCBO.
I am missing the point of how to get the query above on the form and how to get the combo box to change the data.

My combo box source is  CustT.CustID.

Any Ideas?