Note: Some of the syntax may be wrong as I am doing this off the top of my head.
I would create the main report with just the CI_Item table. The item parameter will select the items. I would then add a subreport that has the AR History files. Pass in the date range (probably need to create two formulas, BegDate = Minimum({?DateRange}), EndDate = Maximum({?DateRange}), as subreports do not seem to accept range parameters when passed) to the subreport without linking them to a field. Also link the ItemCode field for the subreport. In the subreport, edit the record selection criteria by adding ""and {AR_InvoiceHistoryHeader.InvoiceDate} in {?@Pm-BegDate} to {?@Pm-EndDate}"". You may also need to use some shared variables to get your totals.