Pivot tables - calculated fields

[Scott]

I can really use some help creating a calculated field within a Pivot table.
I have looked at the calcualted field instructions but I'm having problems
making this work.

Here are my headers:
A1 Acct
B1 State
C1 Sales

Here is my data by cell top to bottom:
Acct in cells A2:A7- HP,Dell,HP,IBM,IBM,HP
State in cells B2:B7- CA,OH,OH,TX,CA,OH
Sales in cells C2:C7- $100,$85,$25,$30,$65,$70

Where I'm at:
I currently have a pivot table with State in the Row, Acct in the Column,
and Sum of Sales in the Data. This gives me a pivot table (or 3x3 matric)
with the state reading down from A5:A7 on a new sheet and HP/Dell/IBM as the
column headers in the B44 range and sales data showing in the range B57.

What I want to add:
I want to essentially insert a column into my pivot table to sum the sales
of HP and Dell and call the sales HP+Dell. Ideally, I'd like to insert this
column in the middle of my pivot table as a new column D pushing IBM over to
column E. How can I sum this data in my pivot table (HP + Dell sales)? How
can I insert a field to take HP sales and multiple by 50% or any other
factor?

Thanks in advance for your help.

-Scott