Removing lines from a text file by matching against substrings

Hello everyone.

I'm approaching this as my first powershell script in trying to both
accomplish something and learn a little powerscript in the process.

Basically I have a decently sized syslog file that I would like to parse
through and remove entries from as I recreate the file. My logfile is a
listing of logins to a group of computers and I want to remove the automated
logins and just see the more interesting ones of people sitting down and
using them. And to be even more ambitious, I'm trying to accomplish this in
a filter so help speed things along a bit and save on some memory as well.

The code I have so far is this:

filter filter-Exclude
{
Param ($Remove)

$result = $_

foreach ($Remove in $ExcludeAry)

{
if (Select-String -pattern $Remove)
{
$result = $null
}
}
$result
}

$Exclude = Get-Content .\Exclude.txt

#New-Item .\results.txt -type file

Get-Content .\CatchAll.txt | filter-Exclude $Exclude


Exclude.txt has the keywords that I want to strip out of the logfile and
catchall.txt is the logfile itself. Since I can't figure out how to have
Select-String return strings that don't match the results, I'm trying to go
the other way and change a positive match to a null so I can write this to
the file without adding additional logic to skip writing it to the file.
And, I should add, I'm not writing to the file right now - my results.txt
file - simply because I haven't gotten things to work right to the console.

Does this make sense? Anyone see a better way to do things (well, working
would be better , but I mean "am I not approaching this with the right
logic?)