How can I run a counter by number of times the script is run

Question

So I've created a script for disabling exchange mailboxes and moving them to a disabled OU in AD.  I currently have this set to run once a week via scheduled tasks but instead would like to kick it up to nightly and improve on the logging.
Right now, the only items I record are the name of the person and the OU they were originally in.  I'd also like to include the groups they were a member of.  I could easily enough include all the groups they were a member of in the email but here
is the twist.
Since we are going to a nightly run of this script, we would want to keep at least a weeks worth of logs in a text file as a just in case.  After a week, the log would be cleared.  I know that would be a counter but I can't even wrap my mind around
how that would work.  Is it even possible?
#Finds all users who have the AD attributes
# wWWHomePage = Updated_by_GroupID
# msExchHideFromAddressLists = True
# msExchHomeServerName not empty
# emailaddress contains @MyDomain.com
# useraccountcontrol = 514 (disabled)
Import-Module ActiveDirectory
add-pssnapin Microsoft.Exchange.Management.PowerShell.E2010
#Declare Variables
$users = $null
$ADgroups = $null
$username = $null
$user = $null
$LogFile = "C:\Scripts\TerminateUsersLogFile.txt"
$LogFile2 = "C:\Scripts\UserNamesMovedtoDisabledOU.txt"
$EmailLogTo = "[email protected]"
#Generates log file
Start-Transcript -path $LogFile
#Performs search for all users in AD filtering only AD user with wWWWHomePage = Updated_by_GroupID, msExchHideFromAddressLists = True, msExchHomeServerName not empty and emailaddress contains @MyDomain.com
$users = Get-ADUser -properties name, emailaddress -Filter {(HomePage -eq "Updated_by_GroupID") -and (msExchHideFromAddressLists -eq $true) -and (emailaddress -like "*@MyDomain.com") -and (msExchHomeServerName -ne "$null") -and (useraccountcontrol -eq "514")}
$users.name -Replace '^cn=([^,]+).+$','$1'
#loops through all users
foreach ($user in $users){
$user.name -Replace '^cn=([^,]+).+$','$1'
#Copies the current OU into the Notes field in the AD User Object.
$newvar = ($user).distinguishedname
set-aduser $user -replace @{info="$newvar"}
# Removes user from all AD groups except Domain Users.
$ADgroups = Get-ADPrincipalGroupMembership -Identity $user | where {$_.Name -ne "Domain Users"}
Remove-ADPrincipalGroupMembership -Identity "$($user)" -MemberOf $ADgroups -Confirm:$false
#Disables their Exchange Mailbox.
Disable-Mailbox -Identity $user.EmailAddress -Confirm:$False
#Moves their AD user object to disabled OU.
Move-ADObject -Identity "$($user.DistinguishedName)" -TargetPath "Disabled Users OU" -Confirm:$false
Write-Output $user.name >> C:\Scripts\UserNamesMovedtoDisabledOU.txt
Stop-Transcript
# Email the log file
$emailFrom = "[email protected]"
$emailTo = $EmailLogTo
$subject = "Terminated Users Cleaned in AD"
$content = Get-Content $LogFile2 | ForEach-Object {$_.Split("`r`n")}
$body = [string]::Join("`r`n",$content)
$smtpServer = "SMTP.MyDomain.com"
$smtp = new-object Net.Mail.SmtpClient($smtpServer)
$smtp.Send($emailFrom, $emailTo, $subject, $body)
clear-content C:\Scripts\UserNamesMovedtoDisabledOU.txt

Answer 1

I apologize for the long delay in replying.  I thank everyone for their help but I'm still running into issues with the script.  Below is the script as it is right now.  I'm having issues with logging as the groups the associate is a member
of are not logging correctly.
#Finds all users who have the AD attributes
# wWWHomePage = Updated_by_GroupID
# msExchHideFromAddressLists = True
# msExchHomeServerName not empty
# emailaddress contains @MyDomain.com
# useraccountcontrol = 514 (disabled)
Import-Module ActiveDirectory
add-pssnapin Microsoft.Exchange.Management.PowerShell.E2010
#Declare Variables
$users = $null
$ADgroups = $null
$username = $null
$user = $null
$LogFile = "C:\Scripts\CleanUpTermedUsers\TerminateUsersLogFile.log"
$LogFile2 = "C:\Scripts\CleanUpTermedUsers\UserNamesMovedtoDisabledOU.txt"
$EmailLogTo = "[email protected]"
#Generates log file
Start-Transcript -path $LogFile
#Performs search for all users in AD filtering only AD user with wWWWHomePage = Updated_by_GroupID, msExchHideFromAddressLists = True, msExchHomeServerName not empty and emailaddress contains @mydomain.com
$users = Get-ADUser -properties name, emailaddress -Filter {(HomePage -eq "Updated_by_GroupID") -and (msExchHideFromAddressLists -eq $true) -and (emailaddress -like "*@mydomain.com") -and (msExchHomeServerName -ne "$null") -and (useraccountcontrol -eq "514")}
$users.name -Replace '^cn=([^,]+).+$','$1'
#loops through all users
foreach ($user in $users){
$user.name -Replace '^cn=([^,]+).+$','$1'
#Copies the current OU into the Notes field in the AD User Object.
$UserOU = ($user).distinguishedname
set-aduser $user -replace @{info="$UserOU"}
# Removes user from all AD groups except Domain Users.
$ADgroups = Get-ADPrincipalGroupMembership -Identity $user | where {$_.Name -ne "Domain Users"}
Write-Output $user.name >> C:\Scripts\CleanUpTermedUsers\UserNamesMovedtoDisabledOU.txt
write-output $ADgroups.name >> C:\Scripts\CleanUpTermedUsers\UserNamesMovedtoDisabledOU.txt
echo $ADgroups.name
Remove-ADPrincipalGroupMembership -Identity "$($user)" -MemberOf $ADgroups -Confirm:$false
#Disables their Exchange Mailbox.
Disable-Mailbox -Identity $user.EmailAddress -Confirm:$False
#Moves their AD user object to disabled OU.
Move-ADObject -Identity "$($user.DistinguishedName)" -TargetPath "Disabled OU" -Confirm:$false
Stop-Transcript
# Email the log file
$emailFrom = "[email protected]"
$emailTo = $EmailLogTo
$subject = "Terminated Users Cleaned in AD"
$content = Get-Content $LogFile2 | ForEach-Object {$_.Split("`r`n")}
$body = [string]::Join("`r`n",$content)
$smtpServer = "smtp.mydomain.com"
$smtp = new-object Net.Mail.SmtpClient($smtpServer)
$smtp.Send($emailFrom, $emailTo, $subject, $body)
Get-ChildItem -Path C:\Scripts\CleanUpTermedUsers\* -Include *.log | where-object { $_.LastWriteTime -lt $((Get-date).Adddays(-7))} | clear-content C:\Scripts\CleanUpTermedUsers\TerminateUsersLogFile.log
Clear-Content c:\Scripts\CleanUpTermedUsers\UserNamesMovedtoDisabledOU.txt