Remove 'Normal' pay rate and choose a pay rate instead

Some of our staff have office hours as their 'normal' hours, and others have teaching hours as their 'normal' hours, so it makes it difficult to separate these when it comes time to process payroll. Instead of filling in a dollar amount on the staff member summary page, can it instead be a 'Default Pay Rate' dropdown where we can select 'office' or 'teaching' (or whatever other pay rates that we have set up).