This card was written by Kristin Snow.
 
You may want the users of your report to be able to choose multiple values for the parameter that selects records in the report. For example, the user may want to choose more than one working list on which to base the report. Here's how.

(The instructions are for converting a single-value parameter a multiple-value parameter.)

1.  In your parameter field, check Allow Multiple Values. The field is now an array. (NOTE: to allow user to type in characters that cause the drop down list to scroll, check Allow editing of default values when there is more than one value. I think this does allow the user to enter names that aren't in the list, however.)

2. Change your record or group selection formula to {field} IN {?parameter_field} rather than {field}= {?parameter_field}. NOTE: You cannot use a function intended for a single value on a multiple-value parameter field without looping through the array. 

3. Depending on how your report and table links are set up, you may need to take care of duplicate records that can result from using a multiple-value parameter. Two options are to 1) add a group or 2) use Suppress Duplicates. 

4. To show the list of values on the report, add a formula field with the following formula: Join({?parameter_field},", "). The Join function comes with CR 8.0 and higher and works like our delimlist. You can enter whatever delimiter you like between the quotes.

5. You can now put the formula field into your report.