The exchange rate changes every day, let alone for a month. If you want to know the exchange rate of Japanese yen against RMB on a certain day in August 2009, you can use the following methods:

Baidu search "China Bank", click to enter official website.

Select "China Bank's Foreign Exchange Quotation" at the bottom of the webpage, select the time and commodity comparison type, and click Query.

(The picture shows the exchange rate of 100 yen against RMB. )