Nested IF Statements

I'm unable to execute the query below. Is there a limit on nested IF's? I get the error "Expression is too complex".

iif(Delivery_Status = ' ' or Delivery_Status is null,'Missing Data'
      ,iif(Expected_Date < Ready_Date,'Bad Settings'
            ,iif(Create_Date > Order_Date,'Bad Entry'
                  ,iif((abs(actual_days - sys_days)>1)
                        ,iif(Loc <> Primary_Loc,'Bad Loc'
                              ,iif(used_type <> Primary_Type,'Bad Type'
                                    ,iif(hours>48,'Too long'
                                          ,iif(Actual_Pickup_Date <> Sched_Pickup_Date and Actual_Pickup_Date is not null and Sched_Pickup_Date is not null
                                                ,iif(Actual_Pickup_Date < Sched_Pickup_Date,'Early Pickup'
                                                      ,'Late Pickup'
                                                )
                                                ,iif((actual_days - sys_days)<-1, 'Fast Transit'
                                                      ,iif((actual_days - sys_days)>1,'Slow Transit','Unknown')
                                                )
                                          )
                                    )
                              )
                        )
                        ,iif(actual_days < sys_days,'Fast Transit'
                              ,iif(actual_days > sys_days, 'Slow Transit','Unknown')
                        )
                  )
            )
      )
);