Bonus paid out of the regular payroll

Hi,

I have the following case:

At the end of every year my company pays to all employees half a salary like a bonus.

This additional payment is done out of the regular payroll (on 15th of December).

The amount that is given is not fixed meaning that the amount paid is based on the days the employee was onsite (based on his timecards) and also a percent is applied as deduction.

So, I made the appropriate setup (using DBAs), but my question is whether there is a way to run a payroll that calculates only these bonus payments and not at the same time the payments of the regular employees’ salary as these payments are done at the end of the month through the regular payroll.