Just open one table only and then click on the [SQL] button and paste the SQL query statement you want to use as there's no releationship between BillItemLine and InvoiceLine.

Queries like:

Select BillItemLine.ItemLineItemRefFullName as Part,
BillItemLine.ItemLineDesc as "Desc", max(BillItemLine.TxnDate) as LastPurchased,
BillItemLine.ItemLineQuantity as PurchQTY,
max(InvoiceLine.TxnDate) as LastSold, InvoiceLine.InvoiceLineQuantity as SoldQTY,
{fn CURDATE()} - {fn CONVERT(BillItemLine.TxnDate, SQL_DATE)} as DaysInStock
from BillItemLine, ItemInventory, InvoiceLine
Where BillItemLine.ItemLineItemRefListID =  ItemInventory.ListID
and BillItemLine.ItemLineItemRefListID = InvoiceLine.InvoiceLineItemRefListID
and BillItemLine.TxnDate > InvoiceLine.TxnDate
group by BillItemLine.ItemLineItemRefFullName, BillItemLine.ItemLineDesc,
BillItemLine.TxnDate, BillItemLine.ItemLineQuantity, InvoiceLine.TxnDate,
InvoiceLine.InvoiceLineQuantity

can not be graphically represented in MS Query.