How do I make sure my email button in gnome launches a new version of ?

1. Right-click the application-launcher for email, which is configured to Thunderbird. This is the mail button on the bottom (could be top) panel.
2. Choose properties
3. In the field that says "Command", change from:
/usr/freeware2/thunderbird/1.5.0/Linux/thunderbird
to
/usr/freeware2/thunderbird/2.0.0.6/Linux/thunderbird