Payroll Exception and Hourly

Solomon Dynamic 6.5

We currently have all of our Salary employee's set up as Exception in the 
pay info tab in Payroll/employee maintenance.  We have some project coming up 
that we want to have these employee's working on in which they would get 
payed the same salary rate that they would normally get

But, when they work on these projects they would get an additional Hourly 
rate on top of this amount.  

We were wondering if there was any way of doing this in the system or do we 
have to have the employee enter an expense report for the hours that they 
worked on this project.

Thanks,