Google Checkout and real time shipping rates

I installed Zen Cart 1.3.7.1, Google Checkout mod 1.4.1 beta, Fedex 1.3.5.a.

I configured Fedex mod and USPS for real time rates, which I hoped I could use for GC too, but on GC page for the shipping options I choose I only saw the values I configured in "Default Values for Real Time Shipping Rates" (that mean default 1), and not real time calculated values.

After hours of struggle, I find out and installed Google Checkout mod v1.4.5_CCS, which allow Carrier Calculated Shipping, but that one works only for domestic shipping, or I need it for international orders.

So, can anyone tell me what module should I use and how to configure it in order to have Google Checkout use real time calculated rates from Fedex and USPS?

Any help will be greatly appreciated.