Down Payment not Exceeding PO value

PO value 1 USD ( Transaction currency) 14000 IDR ( Company code currency)

At the time of Payment table rate 1 USD = 15000 IDR

Need to put in place control of DP can’t exceed PO value at Transaction Currency/Document Currency.

Do we have :

1) Any Standard functionality to handle this?

2) Tolerance of say 2% based on Exchange rate fluctuation?

Pls Adv