Taxable and Non Taxable Wage Types Split

Hi Guys, good morning to everyone, I will appreciate if you can help with the following issue I currently have:

My client wants to split some Wage Types in the system, the situation is as follows:

As Is:

WT´s Paid:

     /4xx   - Bonus Exempt    --   $1,000.00

     20xx  - Bonus Paid         --   $9,000.00

To Be:

     /4xx   - Bonus Exempt    --  $1,000.00

     20xx  - Bonus Paid         --  $9,000.00

     80xx  - Bonus Paid Tax  --   $8,000.00

So, in this case, I have to create a new WT, and that WT should reflects the difference between the WT Tax Exempt and the  WT Paid, so, could you tell me what should I do?, is it possible to create a rule for this?, I will appreciate so much your precious help on this.

Best Regards.