Just change your paramter to allow for multiple values and drop the use of the comma.

Will be easier for your end users that way too.

Again, the easiest and IMO best solution is to NOT use a comma seperated input process but rather edit the parameter to allow for multiple values.

 

Select Edit on the param and in the Options box at the bottom of the screen there is a "Allow multiple values". Change that to TRUE.

 

That is how Crystal is designed to to accept multiple values in a parameter so use its features whenever you can.

Usually a Join() would work but I think it has to be a string and not numeric.

Try a new post on this (specifically state you have an numeric array that can have multiple values with the 999 caveat and how you want it dispalyed in your header) and see if someone can help you with it. I think it needs to be an array which I do not do.