Retrieve the days of a month which are not populated in a column

The following query retrieves the days of a particular month which are not used in a particular column.
Please change the column name and tablename alongwith the month and year to give expected results. Also this can be used to create a function or procedure by replacing the variables by parameters.


Create table #t1
(
checkdate datetime
)

DECLARE @checkdate AS DATETIME;
DECLARE @month AS varchar(2);
DECLARE @year AS varchar(4);
DECLARE @tablename AS varchar(100);
DECLARE @columnname AS varchar(100);

set @month = '06'
set @year = '2008'
set @tablename = 'tablename'
set @columnname = 'columndate'
select @checkdate = Convert(DATETIME,(select @year + '-' + @month + '-01'))


--select @checkdate

WHILE MONTH(@checkdate) = @month
BEGIN
insert into #t1
select @checkdate ;
select @checkdate = dateadd(dd,1,@checkdate) ;
END

execute ('select DAY(checkdate) , checkdate from #t1' +
' LEFT JOIN ('+
'select distinct DAY('+ @columnname+') as [d1] from '+ @tablename +'
where YEAR('+ @columnname+') = '+ @year +' and MONTH('+ @columnname+') = '+ @month +
') split '+
'ON ( day(#t1.checkdate) = split.[d1] ) '+
'where split.[d1] is NULL '+
'order by checkdate' )


/*
select DAY(checkdate), checkdate from #t1
where DAY(checkdate) not in (
select distinct DAY(columnname) from tblsplitmthis
where YEAR(columnname) = @year and MONTH(columnname) = @month
) from #t1
*/

drop table #t1