Problem w/ calculations in the Pager Footer

[snickerB]

I am creating a report to record and provide information on how long a water
pump station has been operating over the last 45 days. I have created the
form to enter the information (on a weekly basis), a table to store the
information, a query to extract the last 45 days of information and a report
to display the last 45 days of information to the end user. But I don't seem
to be able to get access to complete the calculations needed in the Page
Footer of the report to display the the difference between the last two
entries and the average difference over the last 30 days of operation. The
report looks like this:

Report Header -
Station ID information
Page Footer- Field ID's
Date - Time (24hr) - Accummulate run time - (the rest in not needed for
calculation)
Detail - OUTPUTS
Date - Time (24hr) - Accummulate run time - and so on
Page Footer -
(unbound) =dateDiff(), (unbound) =Diff([Accum])
(unbound) =Avg([Accum])


Each time I try different variations of the equations and I keep getting the
same errors. Either #Error or #Name.

I'm frustrated
Bart