Thanks David. I have wrapped all the calculated fields that may return nulls in the Nz() function and I am still getting the same #Error. Here are my new calculated fields:
FallVolume: Nz(FormatNumber(DLookUp("[Volume]","[tblTankGaugeCharts]","[DipDepth]=" & [FallDipReading] & "And [TankID]="...