adding another condition to froumla

this is my foumula

=IIf(IsNull(DLookUp("[qryVouchersSoldToDayTotals]![Total]","qryVouchersSoldToDayTotals","[qryVouchersSoldToDayTotals]![Show Type] =" & nz(" [showtype]",0))),0,(DLookUp(" [qryVouchersSoldToDayTotals]![Total]","qryVouchersSoldToDayTotals","[qryVouchersSoldToDayTotals]![Show Type]=" & nz(" [showtype]",0))))

i need to add [computer] to it so it would link on [show Type] and [computer]

how do i add this and where so it has to match both