Here's the part with instructions:
1) Go here:
http://www.weatherroom.com/cgi-bin/...ass&pass=tafINT
2) Select your country and city
3) Click "display Forecast/Conditions"
4) Top right you will see this "ICAO Used:" followed by a code - Place this code in your zip code field and you will see your local international forecast.
And here's a link to the hack thread:
http://www.vbadvanced.com/forum/showthread.php?t=1012