automatically update another field based on other parts of the record

Sql is not a strong point with me so I'm just going to throw this out there. I have a stored procedure that updates the quantity in my 'CartItems' table. Is there a way to have something else happen within the stored procedure that will update another field based on other parts of the record? There is a 'lineTotal' field that I need to equal the 'pounds * itemSell' fields which are both fields within this record.

CREATE PROCEDURE UpdateCartItem
(
@.cartItemID Int,
@.newQuantity numeric(9)
)
AS
UPDATE CartItems Set quantity = @.newQuantity
WHERE cartItemID = @.cartItemID
GO

sure. you can update as many fields as you want within the UPDATE statement.

CREATE PROCEDURE UpdateCartItem
(
@.cartItemID Int,
@.newQuantity numeric(9)
)
AS

SET NOCOUNT ON

UPDATE
CartItems
Set
quantity = @.newQuantity
,lineTotal =pounds * itemSell
WHERE
cartItemID = @.cartItemID

SET NOCOUNT OFF

GO

|||Or make the lineTotal a computed column. Just modify the table and tell it the lineTotal column is equal to pounds*itemSell.sql