Fiscal/Financial Year Comparison SQL

Hi EE,
I’m trying to create a stored procedure that will get the total value for the Financial Year to Date by customer, but then I want to show the previous Financial Year to Date as well for comparison.
So take today (July 9th 2012) I want to get all the values from (May  1st 2012 to July 9th 2012) for Current Financial Year .
So last year would run from (May  1st 2011 to July 9th 2011) to make an accurate comparison.

Our Financial Years always run from (May 1st to the following April 30th)

Below is a mock up picture of what i'm trying to achieve.

i seem to be going round in circles....

ECLARE @CurrentFinancialYear	as Int
DECLARE @LastFinancialYear		as Int
SET		@CurrentFinancialYear	='2012'
SET		@LastFinancialYear		='2011'

Select				invoicedate												As [FullDate],
					customer.name											As [CustomerName],	
					InvoiceHead.fiscalyear									AS [FinancialYear],
					InvoiceHead.fiscalperiod								AS [FinancialYear],
					DATENAME(MONTH,InvoiceHead.invoicedate)					AS [FinancialMonthName],
					(dbo.invcdtl.sellingshipqty * dbo.invcdtl.unitprice)	AS [Value]
					
					
from				  dbo.invchead as InvoiceHead 
		INNER JOIN
                      dbo.invcdtl ON InvoiceHead.invoicenum = dbo.invcdtl.invoicenum
        INNER JOIN
                      dbo.customer ON InvoiceHead.custnum = dbo.customer.custnum
					

where	InvoiceHead.fiscalyear = @CurrentFinancialYear 
		
order by fulldate

Select allOpen in new window

Thank you for your Help....

Ross