LIM Workforce Planning (WFP) - excluding register columns for specific Groups

Hi all, 

Is it possible to exclude certain register columns for specific Groups?  For example, not requiring input or displaying an “Hourly Rate” column for full time salaried employees.  In this case an Employee Type is a separate register column identifying employees as full time, part time, or contract. Filter groups are set up by Employee Type and calculations only run for the relevant groups.

In the case above, the Hourly Rate column could just be left blank, but how are others handling cases where there is a control list attached to a register column, but that register column is only applicable to some employee groups?  I would rather not have an “N/A” or similar option in the control list, which would allow this as a selection for employees who should have a “real” control list value assigned to them.

TIA