Doesn't Gmail have a create event from email function so you don't have to bop back and forth?

Also if you're using Thunderbird to POP mail... you can also get Sunbird to control your Google Calendar(s) and then the Lightning Add-on for Thunderbird which pulls in the Sunbird info (One of these days I'm sure they'll finally more easily merge Thunder and Sun, but until then this is the way to get Thunderbird as close to Outlook as possible).

</tech evangelizing>