Is there a way, using OLAP, to have a summary level report that uses averages, and allows the user to drilldown to the detail records? One scenario would be a report that shows average daily sales by region for March, and the drill down would show the actual sales by day for March.

Mac,
My experience w/ OLAP is that you are seperating the dimension from the metrics so you typically "drill" on dimensions to show the next level of dimensional(like Year to Quarter to Month to Week to Day, etc) metrics(sum , average, max, whatever). I did this within the report code but you could setup the dimensional hierarchy within the masterfile. I've never tried using a metric type field as part of an olap hierarchy.

-OLAP ON
OLAP DIMENSIONS
HIERARCHY: REG_NAME,SUBMIT_DATE,NUMBER;
END
TABLE FILE ACTIV8X
IF DIV_ID EQ 'I004'
IF SUBMIT_DATE GE '04012008'
SUM ACCAPP (you can make this Average)
BY REG_NAME
ON TABLE SET PAGE-NUM OFF
ON TABLE SET LINES 99999
ON TABLE SET AUTODRILL ON
ON TABLE SET OLAPPANE TOP
END

ok, so with your code, if you had an average, when you get the "Number" dimension, you would still have an "average" measure, correct?

yes. that "number" in the hierarchy is the account number, which I made part of the hierarchy so when you drill from reg_name (region in my system) to submit_date (account disposition date) you get the detail. You could also create add'l measures on the fly .
TABLE FILE ....
SUM AVE.ACCAPP
ACCAPP NOPRINT
BY...
END
The user can then turn on or off the measure(s)from the OLAP panel

but is there a way to drill down through averages, then at the "lowest" level of the hierarchy, you get the detail records, not an average?