Asset Foreign Exchange Gain/Loss adjusted in Assets during Vendor payment

Dear,

My Indian client is requires Foreign Exchange Gain or Loss should be adjusted to Asset Accounting during Vendor Payment?

Can any one suggest me how to achieve this result?

For Example,

During PO creation, 1 Eur = 85 INR

During MIRO posting 1 EUR = 90 INR.

How to post Foreign Exchange Gain or Loss adjustment to assets during Vendor Payment posting?

Regards,

M.Mohan.