VRS Exemption 5Lakh to be provided through custom wagetype

Dear Consultants,

We have created a new wage type under Infotype 15 to pay the VRS money to employee, according the Govt rule up to 5 Lack slab to be provided as non taxable and more than 5 lack is taxable which now i want create, please let me know which processing and cumulation calass need to be changed for this wage type.

Thanks In Advance,

Navesh