Control activity is a recognised gauge of pilot workload and recent research has employed wavelet decomposition to classify discrete control actions into categories such as guidance and stabilisation. The aim of the present work is to extend the wavelet approach so that workload may be quantified through sets of rules based on appropriate control activity metrics. The rules are derived from data collected in piloted simulation trials of a variety of flying tasks involving a number of pilots and different helicopter configurations. Statistical tests are then applied which test the efficacy of the derived rules. The immediate aim of the research is to establish whether workload can be successfully predicted from control responses. The underlying goal however, is to be able to predict workload ratings from desktop simulations in order to provide indicative workload information at the design stage. The contribution of the current study to this objective is discussed.