Payroll - Journalling between categories.

Hi all.

So,  I have two major payroll categories set up, both go to Gross pay, 

One is Base Hourly, the other is Manufacturing Hourly.

Manufacturing hours overrides  to COG

I need to move hours for some employees from base hourly to manufacturing hourly, so i can account for their work on production floor.

How do i best do this?  I need to go back to July 1st,  I have done an audit on the payroll and what needs to be moved for each employee, if i have to do a GJ it is in dollar value,  anyway i can do it somwhere as hours, not dollars.  

I am assuming it will be in payroll, but how much of a head ache will it be.  Can i do one transaction for each employee for each month???   Nothing will change monetarily.   

so happy to do this this time of year.......

Thanks in advance