Cómo pasar los parámetros a laEXEC sp_executesql declaración correctamente?

Esto es lo que tengo ahora, pero recibo errores:

alter PROCEDURE [dbo].[usp_getReceivedCases]
    -- Add the parameters for the stored procedure here
    @LabID int,
    @RequestTypeID varchar(max),
    @BeginDate date,
    @EndDate date
AS
BEGIN
    -- SET NOCOUNT ON added to prevent extra result sets from
    -- interfering with SELECT statements.
    SET NOCOUNT ON;


declare @statement nvarchar(4000)

set @statement = N'select   SentToLab,
FROM     dbo.vEmailSent
WHERE     SentToLab_ID=@LabID and convert(date,DateSent) >= @BeginDate 
and CONVERT(date, datesent) <= @EndDate
and RequestType_ID in ( @RequestTypeID )

EXEC sp_executesql  @statement,N'@LabID int',  @LabID, N'@BeginDate date', @BeginDate,N'@EndDate date', @EndDate, @RequestTypeID=@RequestTypeID

END

RequestTypeID es una lista de enteros delimitada por comas, como esta: "1,2,3,4,5"

aquí está mi intento # 2, también sin éxito

declare @statement nvarchar(4000)

SET @statement =' select    SentToLab_ID

FROM     dbo.vEmailSent
WHERE     
SentToLab_ID='+@LabID+' and convert(date,DateSent) >= '+@BeginDate +'
and CONVERT(date, datesent) <= '+@EndDate+'
and RequestType_ID in ('+ @RequestTypeID+' )
group by FileStream_ID, SentToLab_ID'


EXEC(@statement)

Operand type clash: date es incompatible con int