Find maximum number between two dates

hi

i am using sql server 2005.

i have table

tbl_cashcounter

CREATE TABLE [dbo].[tbl_CompanyMaster](
	[CompanyID] [int] NOT NULL,
	[Name] [nvarchar](100) NULL,
	[YearStart] [datetime] NULL,
	[YearEnd] [datetime] NULL,
	)
this table has always only one row
CompanyIDName                       YearStart        YearEnd
2        Fotofash Color Lab & Studio2014-04-01 12:00:00.0002015-03-31 23:55:49.000


CREATE TABLE [dbo].[tbl_CashCounter](
	[Id] [int] IDENTITY(1,1) NOT NULL,
	[BillNo] [nvarchar](50) NULL,
	[BillDate] [datetime] NULL )

there is Bill Format

strar yeear ( 14) endyear(15) department serial No.

yyyyDp-xxxxxx1

1415-vd-000001

1415-vd-000002

1415-ST-000001

1415-ST-000002

i am looking sql function which will return max number  between  YearStart andYearend with respect department

i have witten the query

select MAX(Right(BillNo,6)) AS no
from tbl_CashCounter,tbl_companymaster
 WHERE (SUBSTRING(BillNo, 5, 2)) = 'vd' 
 and  billdate  
 between  yearstart and  yearend

but it's not working.

please help me.

note : i am using sqlserver 2005

Thanks Best Regard Naweez