Powershell 2.0 write back to xlsx - excel

Question

Cross post from powershell.org..
I am trying to have Powershell read an xlsx for username info, convert to a csv (to be imported) and then write back something to the xlsx so next time it won't reimport the same users.
I don't want to delete the users in the xlsx but am thinking to add a date column or some other data maybe the word "created" and have powershell write this data in an available column. But then I would have to have my script ignore this new column if contains a old date or the word created?
<br> Current xlsx columns headers
<br> A B C
<br> 1 Full Name, Personal Email, "write back data"
<br> 2 John Doe Jdoe#gmail.com, Created (Sample write back data)
<br> 3 Don Juan Djuan#gmail.com, Date Imported (sample write back data)
Convert to csv code (This part is working fine.)
$File = "C:\Scripts\Excel\Accounts.xlsx"
$Savepath1 = "C:\Scripts\Csv\Employee Accounts.csv"
$SheetName1 = "Employee Accounts"
$ObjExcel = New-Object -ComObject Excel.Application
$Objexcel.Visible = $false
$Objworkbook=$ObjExcel.Workbooks.Open($File)
$Objworksheet=$Objworkbook.worksheets.item($Sheetname1)
$Objworksheet.Activate()
$Objexcel.application.DisplayAlerts= $False
$Objworkbook.SaveAs($SavePath1,6)
$Objworkbook.Close($True)
$ObjExcel.Quit()
Here is my current import-csv code
$EmployeeAccounts = Import-Csv $savepath1 | Where-Object { $_.Fullname -and $_.PersonalEmail}
Things to consider:
There might be additional concatenated info in additional fields added to the xlsx. Therefore excel might count these as used rows if the fields have formulas in them. So I only want to write the data to the new column if there is a username and email address in columns A & B.
Thanks!

Answer 1

To be honest it's going to be simpler to import the whole thing, perform your process filtering for entries that don't have anything in the Updated field, update the "Updated" field for each entry that you processed, and then just write the entire thing back to the file. So, something like:
$Users = Import-CSV $FilePath
$Users | ?{[String]::IsNullOrEmpty($_.Updated)} | %{
Do stuff here
$_.Updated = Get-Date
}
$Users | Export-CSV $FilePath -Force -NoTypeInfo
Edit: Well then, that does complicate things a little bit. So, this one does take a plugin, but it's a plugin that I whole heartedly feel should be included in almost any installation that's functionally used regularly IMHO. The PowerShell Community Extensions (PSCX) can be gotten from pscx.codeplex.com and will grant you access to the command Out-Clipboard which is awesome for what you want to do.
$Users = Import-CSV $FilePath
$Users | ?{[String]::IsNullOrEmpty($_.Updated)} | %{
Do stuff here
$_.Updated = Get-Date
}
$Users | Select Updated | ConvertTo-CSV -Delimiter "`t" -NoTypeInformation | Out-Clipboard
$SheetName1 = "Employee Accounts"
$ObjExcel = New-Object -ComObject Excel.Application
$Objexcel.Visible = $false
$Objworkbook=$ObjExcel.Workbooks.Open($File)
$Objworksheet=$Objworkbook.worksheets.item($Sheetname1)
$Objworksheet.Activate()
$Range = $Objworksheet.Range("C1","C1")
$Objworksheet.Paste($Range, $false)
$Objexcel.DisplayAlerts = $false
$Objworkbook.Save()
$Objexcel.DisplayAlerts = $true
$Objworkbook.Close()
$Objexcel.Quit()
[void][System.Runtime.Interopservices.Marshal]::FinalReleaseComObject($Objexcel)
That will paste your data, header included, into column C.