Need Help With Query -- Sales Data By Customer.GroupCode In Monthly Columns

I'm trying to develop a query that provides sales data by Customer.GroupCode in monthly columns as depicted below:

GrpCd JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC TOT
Film 5,000 15,000 20,000
Aero
Elct 3,000 950 3,950
Desg
Edu 150 150

Here€™s a simplified version of the DDL:
CREATE TABLE invchead (
invoicenum int NULL ,
invoicedate datetime NULL ,
invoiceamt decimal(16, 2) NULL ,
custnum int NULL )

CREATE TABLE customer (
custnum int NULL ,
groupcode varchar (4) NULL )

The query below gets me close but it gives me gives me one row for each customer. So if I have 5 customers with the same group code, I get 5 rows for that group code. I need to modify it or come up with a different approach that gives me only one row for each GroupCode.

SELECT distinct
c.Name,
c.GroupCode,
(SELECT SUM(InvoiceAmt) FROM InvcHead WHERE InvcHead.custnum=i.custnum AND DATEPART(year, InvcHead.invoicedate)= DATEPART(year, i.invoicedate) AND DATEPART(month, InvcHead.invoicedate)=1) JAN,
(SELECT SUM(InvoiceAmt) FROM InvcHead WHERE InvcHead.custnum=i.custnum AND DATEPART(year, InvcHead.invoicedate)= DATEPART(year, i.invoicedate) AND DATEPART(month, InvcHead.invoicedate)=2) FEB,
......
(SELECT SUM(InvoiceAmt) FROM InvcHead WHERE InvcHead.custnum=i.custnum AND DATEPART(year, InvcHead.invoicedate)= DATEPART(year, i.invoicedate)) TOT

FROM InvcHead i INNER JOIN Customer c ON (i.custnum=c.custnum)
WHERE i.invoicedate>='1-1-2007' AND i.invoicedate<'1-1-2008'

Grateful for any advice that will get me closer to accomplishing this.

Thanks