The use of table-valued parameters in SQL Server 2008 removes the need for these comma separated parameters.

But if you need something like this you could use a CLR function or use something like this:

--select * from [System].[tfn_DelimStringToTable]('a,b,c,d,e',',')

CREATE FUNCTION [System].[tfn_DelimStringToTable](@str NVARCHAR(max),@delim CHAR(1))

RETURNS @table TABLE ([ID] INT IDENTITY(1,1),[Column] sysname NOT NULL)

WITH SCHEMABINDING,ENCRYPTION

AS

BEGIN

DECLARE @x XML

SET @x = '<t>' + REPLACE(@str,@delim, '</t><t>') + '</t>'

INSERT INTO @Table([Column])

SELECT x.i.value('.', 'NVARCHAR(MAX)') AS token

FROM @x.nodes ('//t') x(i)

RETURN

END