PowerShellによりExcelの各シートの先頭に連番を振るサンプルコード

$excel = New-Object -ComObject Excel.Application
$book = $null

$excel.Visible = $false
$excel.DisplayAlerts = $false

$fileName  = "book.xlsx"
$filePath = (Convert-Path .) + "\" + $fileName

$book = $excel.Workbooks.Open($filePath)

for ($i=1; $i -le $book.worksheets.Count; $i++){

    $newSheetName = $i.ToString("00") + "_" + $book.worksheets($i).Name
    $book.worksheets($i).Name = $newSheetName

}

[void]$book.Save()
[void]$book.Close($false)
[void][System.Runtime.Interopservices.Marshal]::ReleaseComObject($book)

[void]$excel.Quit()
[void][System.Runtime.Interopservices.Marshal]::ReleaseComObject($excel)

Pause