Generating temporary tables in Access

[creed]

Is there a way to reference data that has is in another row.

For example:

Round(([NetSales]-[LastYearNetSales])/[NetSales]*100,0) AS NetSalesIncrease

Here i want to reference the data in this years row(NetSales) and also the data
in field LastYearNetSales in the previous year's row. I first though of a where
statement, but since it's in a select statement, it didnt like it. Anyone have
any thoughs?

Also is there a way to have only certain field show up, while still havign the information avialble for access to do it's work in the background calculating the math operations like what i've mentioned above?