Average Times

[mwake]

I am using CR2011 with a SQL Server database as my data source. I am trying to come up with an average response time per week, but have run into problems. I created a formula called Response Time to calculate the difference between order date/time and arrival date/time (DateDiff("n", {@Order Date}, {Haillogs.Date}). The Order Date formula adds 7 hours to the order date because of time zone differences in date/time fields. I can't use the average summary function on the @Response Time formula because there are more than 1 record for each order, which makes the denominator too big. However, when I tried summing the Response Time formula then dividing by my @Session ID field, I come up with odd numbers because the sum of @Response Time is numeric and not date/time. How do I get a group average of time when I cannot divide by the sum by the number of records within the group??