Retroactive Payroll for Fixed 30 days

Dear Frndz,

I have a requirement, where retroactive Payroll has to be performed on default for 30 days

We are working for Saudi Arabian Payroll, Hijri Months, so it has 29 days in one month and 30 days in another month respectively.

Need to calculate Retroactive, Say for instance

An employee Payroll is ran for period 04/1433 (04 month has 30 days) , Then we are creating  an allowance in Infotype 14 for 1000 Riyals from date 15/03/1433 (03 month has 29 days).

System should give retroactive amount as 500 riyals, but its providing 517.24 (1000/29 * 15)

I want the system should use 30 days default for all scenarios in arrears, LOP etc

Thanks in Advance

Regards

L S