Powershell - add multiple columns to multiple excel files - powershell

Question

I have a folder that has over 50 excel files in it ("Project dump' in the path below.) All of these files contain the same exact data (its archived monthly data that's used for a MoM report) I need to update all of these files to add 10 new column headers - none of these columns will have any data in them, they just need to be added to the table to match the most current month extract that will have data in it going forward.
I've been using Powershell, and have a script that can add one column to one file at a time, but it would honestly be faster for me to manually open each file and add the columns myself. I cant seem to figure out how to change my script to do what its doing to multiple files (and with multiple columns), any help would be greatly appreciated!
background; the reference is a specific file in my project dump folder. Column 50 is the first blank column, that needs to be added to the table:
(Get-ChildItem "C:\Downloads\Project dump\ArchiveJAN21.xlsx")|
foreach-object {
$xl=New-Object -ComObject Excel.Application
$wb=$xl.workbooks.open($_)
$ws = $wb.worksheets.Item(1)
$ws.Columns.ListObject.ListColumns.Add(50)
$ws.Cells.Item(1,50) ='Call Type'
$wb.Save()
$xl.Quit()
while([System.Runtime.Interopservices.Marshal]::ReleaseComObject([System.__ComObject]$xl)){'released'| Out-Null}
}

Answer 1

You need to define the Excel object before the loop and quit afterwards.
Also, use Get-ChildItem to get FileInfo objects from a folder path, not a hardcoded path to a file.
Try:
# an array with the new column names
$newColumns = 'Call Type','NewCol2','NewCol3','NewCol4','NewCol5','NewCol6','NewCol7','NewCol8','NewCol9','NewCol10'
# create the Excel object outside of the loop
$xl = New-Object -ComObject Excel.Application
$xl.Visible = $false
# loop thtrough the files in the folder
(Get-ChildItem -Path 'C:\Downloads\Project dump' -Filter '*.xlsx' -File ) | ForEach-Object {
$wb = $xl.WorkBooks.Open($_.FullName)
$ws = $wb.Worksheets.Item(1)
# get the number of columns in the sheet
$startColumn = $ws.UsedRange.Columns.Count
for ($i = 0; $i -lt $newColumns.Count; $i++) {
$startColumn++ # increment the column counter
$ws.Cells.Item(1, $startColumn) = $newColumns[$i]
}
$wb.Close($true) # $true saves the changes
}
# quit Excel and clean COM objects from memory
$xl.Quit()
# clean up the COM objects used
$null = [System.Runtime.Interopservices.Marshal]::ReleaseComObject($ws)
$null = [System.Runtime.Interopservices.Marshal]::ReleaseComObject($wb)
$null = [System.Runtime.Interopservices.Marshal]::ReleaseComObject($xl)
[System.GC]::Collect()
[System.GC]::WaitForPendingFinalizers()