Split like function in SQL SERVER 2000

ALTER PROC dbo.USP_GET_OPERATOR_CHAT_MESSAGES_TESTING(
@ChatIds VARCHAR(500)
)
AS
--USP_GET_OPERATOR_CHAT_MESSAGES_TESTING '1071,1072'
SET NOCOUNT ON
BEGIN
DECLARE @Str Varchar (100)
DECLARE @tab TABLE (ID INT)
SET @Str = @ChatIds + ',' --'4,5,6,'- pls note the string ends with the delimited char i.e. comma
WHILE @str <> ''
BEGIN
INSERT INTO @TAB (ID)
SELECT SUBSTRING(@Str, 1, CHARINDEX (',', @Str) -1)
SET @str = SUBSTRING(@Str, CHARINDEX (',', @Str) + 1, LEN(@Str) - CHARINDEX (',', @Str))
END

SELECT MessageID, IsOperator, Message FROM tblChatMessage
WHERE ChatId IN (SELECT * FROM @tab) ORDER BY ChatID, MessageID
END