China 's RMB (Yuan) based cross-border trade settlement totaled 2.08 trillion Yuan in 2011, according to People's Bank of China.  Based upon the year end forex rate of 6.3 Yuan per USD, this is equivalent to about $330 billion USD.

China's total export was $1.9 trillion USD last year, and total import was $1.7 trillion.  This means about less than 10% of China's total trade is settled in China's local currency.

China's total export to Asean was $170 billion USD, and import was $192 billion USD last year.  This means China's Yuan settled cross-border trade is roughly equivalent to its total trade with all Asean countries.  It would not be a surprise if the total Asean trade value is surpassed by China's cross-border Yuan settled trade this year.