How To Do Multiple Sums?

Hello All,

I'm trying to do a query to produce multiple sums based on how many rows are in a table.
Here's a sample of the table and data, what I want is to have a query to sum each company's total and display it.




create table #invoices


(
InvoiceNumber varchar(5),
--other info
CompanyCode int,
InvoiceAmount real
)


Insert Into #invoices values('A1000', 1, 1000)
Insert Into #invoices values('A1000', 2, 100)
Insert Into #invoices values('A1000', 3, 300)
Insert Into #invoices values('A1000', 1, 600)
Insert Into #invoices values('A1001', 2, 2000)
Insert Into #invoices values('A1001', 3, 1000)
Insert Into #invoices values('A1001', 1, 300)
Insert Into #invoices values('A1002', 2, 2500)
Insert Into #invoices values('A1002', 3, 2000

I was thinking of doing it something like this:

Select

Sum(case when CompanyCode=1 Then CompanyCode End) as TOTAL1,
Sum(case when CompanyCode=2 Then CompanyCode End) as TOTAL2,

Sum(case when CompanyCode=3 Then CompanyCode End) as TOTAL3
from
#invoices


But I would rather not have to hard code the company numbers in the query as they can be added or removed from the list. Ideally it would take the CompanyCode from the COMPANY table and SUM each companies totals and display it.
Any help on this would be greatly appreciated!
Thanks,