I'm befuddled -- not an uncommon situation for me

If a field contains 500 lines of text, and lines 1 to 25 should be deleted from that field, is there a quick way to "select" those lines as a "chunk" and empty them? I'd like to "hilite" that group of lines without the user needing to use the mouse to do so and then delete them.
It seems some combination of "the selection" and "hilitedLIne" should work, but I'm not figuring it out. Thanks in advance for any help.
Regards,