iphoto on external drive--iphone download 3G

If you have moved your iPhoto database to an external hard drive - with iPhoto on your computers hard drive set up to access the iPhoto database on the external drive, you dont have to do anything. The only options you have under the Photos tab for your iPhone sync preferences is sync or transfer photos from iPhoto, or select a folder on your computers hard drive that contains photos. There is no option under the Photos tab for your iPhone sync preferences to designate where your iPhoto database is stored - this is done with iPhoto.
 MacBook Pro 15" Intel Core 2 Duo/2.53GHz/4GB RAM/500GB HD Mac OS X (10.6.2)  iPod w/Video 30GB,  iPhone 3G 16GB

My ibook has only 10% Hard drive left
and i cant download pics from my I phone ,
So i need to learn how to send pics to external HD without
copying to IbooksHD?