Wage type

Gurus

For Indian Payroll.

A. I have wage types

1000 = Amount

1001=Amount

1002 =Amount

I want to maintain addition of all three wage types in a dummy WT 9001-Gross per month (not included in Payroll,just for display purpose)

B. I want to multiply 9001 by 12 to get Gross per Annum to WT 9002

c.I want to calculate a WT which is 13% of Basic*12

I have few more Requirements like this,Kindly let me know how to do these (Any functional module,User exxit,Badi,BApi)