Get-XlsContentDemo.ps1

$path = "https://<tenant>.sharepoint.com/sites/<site>/<library>/<file>.xlsx"
$worksheetNames = ""
$save = $true

$excel = new-object -comobject excel.application

$timestamp = Get-Date -format "yyyyMMddHHmmss"

try
{
    $workbook = $excel.Workbooks.Open($path)
    if (!$workbook) {continue}
    $workbook.Worksheets | %{
        $_.activate()
        $_.Range('d6').Value2 = $timestamp
        $_.usedrange.rows | %{
            $_.cells | %{
                $_.Value2
            }
        }
    }
}
catch
{
    $_
    $excel.visible = $true
}

$workbook.Close($save)

$excel.DisplayAlerts = $false
$excel.Quit()

if (!$test)
{
    while([System.Runtime.Interopservices.Marshal]::ReleaseComObject($workbook)){}
    while([System.Runtime.Interopservices.Marshal]::ReleaseComObject($excel)){}
}
[System.GC]::Collect()
[System.GC]::WaitForPendingFinalizers()