How to pay domestic suppliers once currency is devalued

Hi All-

  We have a scenario where in we need to make a payment to the domestic supplier invoice once the currency has been devalued but purchasing power remains the same. For Ex- There is an AP invoice for 200 Yuans before devaluation and now Yuan is devalued by 50%. In that we case, we need to pay only 100 Yuans to the suppliers. Has anyone come across similar requirement? All pointers are welcome.

Thanks,

Rahul