says a field is required here. tried with and without parentheses around the concatenation

PthPercentile(90,{@elapsed Time}, ({Call_Types.descr}&{Call_Sources.descr}&{@Zones}))

so now I did that and now it says there must be a group that matches this field. I appreciate all your help by the way! still a little new to crystal and trying to get into some of these advanced functions.

Ok so I have another one I am trying to do. I am returning a count and a percentile for total calls by hour. I am counting the call number (a unique id) for each hour then dividing by date to find average calls per hour. How can i find 90th percentile by hour? the field available are    table.date, table.callnumber, table.calltime