TSQL Help

Does the data going into that field need to be formatted like that or the data pulled from that field in an output query need to be formatted like that?

I need to update the data in the table to that

SELECT CONVERT(varchar, CAST(987654321 AS money), 1)

That does not give me 2,220

create function make_number (@value varchar(40))
returns varchar(40)
as
begin
declare @o varchar(40)
set @o = ''
 while len(@value) > 3
  begin
   set @o = ',' + right(@value, 3) + @o
   set @value = substring(@value, 1, len(@value) - 3)
  end
return @value + @o
end
go
update table_name set field_name = dbo.make_number(field_name)
go

I need another way other that creating a function.. How about where len(field)=4? Would that work

SELECT CONVERT(varchar, CAST(2220 AS money), 1)
--2,220.00
SELECT substring(CONVERT(varchar, CAST(2220 AS money), 1),0, charindex('.',CONVERT(varchar, CAST(2220 AS money), 1)))
--2,220