DLookup Function To Load Information From Table To Another Table Using Subform

I have 3 table table; Invoice table, Product table and Sale_product table. Sale product table records all sale from the product table

Invoice table has these fields
ID
TOTAL
CASH_TENDERED
CHANGE

Product table has

ID
CODE
QUANTITY
NAME
PRICE

and Sale_Product table has these
ID
PRODUCT_CODE
QUANTITY
PRODUCT_NAME
PRICE
SUBTOTAL
INVOICE

I did main form from Invoice table and sub form from Sale_product table. I want to use DLOOKUP function to load the name and price, quantity and calculate subtotal automatically from the product table based on the product code entered. i have being trying hard and i keep on getting "Name? error"