No, and you need to be very carefu.
If you delete photos from an Event you are deleting them from the Library, and that means you're also deleting them from every Album, book, slideshow etc in the Library.
Have you considered having two Libraries? One full one and with a smaller selection?
1. Quit iPhoto.
2. Copy the iPhoto Library from your Pictures Folder to the external drive.
Now you have two full copies of the Library. To choose between them: Hold down the option (or alt) and launch iPhoto. From the resulting menu select 'Choose Library'
3. On the Internal Library, remove the pics you don't want with you all the time.
Now you have one full library on the external and another smaller sub-set on the Internal.
A couple of comments:
a. The external disk needs to be formatted Mac OS Extended (Journaled)
b: When you're removing the unwanted pics from the Internal Library you need to delete them in batches of about 100 or so. Trashing more at one time can cause problems with the database.
Managing Multiple Libraries - including moving pics/albums/rolls and metadata between them - is greatly facilitated by using iPhoto Library Manager