maybe you'll get help from someone more experienced than me, but in the meantime, try this.
go to the first query, qryDistHIVCasesStatsDAC, and add nz to the following fields: BilledDRG,NumberOfCases,AverageLen gthOfStay,CasesReviewed,CasesDenied,AvgOflos
(i don't know what the billing...