Customer item name display ,if item master id exit in

Question

I have item master table in which column are (ItemCode,ItemName,Weight) and second one table is customer item table(CItemcode,CItemName,CustomerID,ItemCode),

third table is customer (CustomerID,CustomerName)

fourth table is Produce item (Prodno,Itemcode,ItemName,Weight,Orderno).

Fifth table salesorder(Ornerno,CustomerID,Qty)

 

Now i want when select record from Produce item table, then item code from item master table, if exit in customer item table then CItemName get display otherwise if item code of item master file does not exit in customer item table against customer then item name display from item master file.

 

please help me..