You can use a data item to input a single discreet parameter value only, not multiple values. This is because Crystal itself does not allow the automation of multiple parameter values.

For automated reports I would suggest that you make a copy of your current report, remove the parameter prompt from the record selection formula and replace it with a query to bring up the data you require. CRD will not require a parameter and the report will show just the data you want.

e.g. instead of {mytable.mycolumn} = {?myparamter} use {mytable.mycolumn} in ["valuea","valueb","valuec"]

Alternatively, you can schedule the one report, but in CRD go to Properties->Parameters and click on Advanced. This will show the record selection formula that CRD has read from the report. Modify the formula in CRD so that the parameter prompt is removed and replaced with a query which brings up just the data which you require for this schedule.

This second method ensures that the change only affects that particular CRD schedule and you can re-use the source report for other things. Also you don't have to maintain multiple versions/copies of the source report.

Hope this helps.