Vista Command Prompt "redirect operator" problem?

I'm using Notepad++ on my Vista machine to edit multiple files at a time. I found a nice program online that is basically the equivalent of the Unix "grep" command. From this, I can use the command prompt to get a list of files matching a criteria. My goal is to open them into Notepad++ to edit.

When I run the grep command, I use:

grep "the text" * >> filename

...to put the filenames, one per line, in the file. I then try this:

"c:\...\notepad++.exe" < filename

...expecting it to load each of the files listed in "filename" into the program. The program opens, but no sign of the files.

Am I missing something? Please help! Thanks, I really appreciate any help you could give.