WHT Tax codes validity period

Dear Gurus,

My query here is, I have a WITHHOLDING TAX CODES AND WITHHOLDING TAX TYPES as follows:

AB & AB with validity period of 01.04.2009 and TAX Rate as: 10%

Know when I want to change the TAX rate to 5% with validity start date as: 01.06.2016.

I can go and change the Validity Period and TAX Rate Percentage from 10% to 5%.

But the concern here is I have some pending documents which I need to post before: 01.06.2016 and the system should pick 10%.

But I don't have the feasibility of configuring the same for the WHT tax codes.

Please guide me.

BR

RR.