Create a string parameter with the three options. Then create a formula like this:
select (?Parameter}
case "Division" : {table.division}
case "Action Date" : totext({table.actiondate},"yyyy/MM/dd")
case "Disposition Date" : totext({table.dispositiondate},"yyyy/MM/dd")
You can either use this as a sort field or use it as a group field. If you want the dates to display in a different format, use the above formula just for sorting or grouping, but add the actual field in the desired format to the group header or body of the report.
-LB