Export to 2nd+ spreadsheet - export-to-excel

Question

I'm using Export-Csv to export [pscustomobject]s. Then I'm using a second function to convert that into a xlsx. Which works perfect. But what if I wanted to export into the second spreadsheet and rename it to something different?
I know Export-Csv doesn't support multi spread sheets.
Function SaveAsXLXS
{
#Hide Old File
(Get-Item $ResultsFilePath -Force).Attributes = "Hidden"
#Opens Old File
$Excel = New-Object -ComObject Excel.Application
$Workbook = $Excel.Workbooks.Open($ResultsFilePath)
#Formating
if ($GroupsTab.IsSelected -or $OrgBoxesTab.IsSelected)
{
$Workbook.Worksheets.Item(1).Columns.Item(1).Font.Bold = $True
$Workbook.Worksheets.Item(1).Columns.Item(1).Font.Size = 12
}
$Workbook.Worksheets.Item(1).Rows.Item(1).Font.Bold = $True
$Workbook.Worksheets.Item(1).Rows.Item(1).Font.Size = 15
$Workbook.Worksheets.Item(1).UsedRange.EntireColumn.Autofit()
#Creates Name for New File
$ExcelOut = $ResultsFilePath -replace '\.csv$', '.xlsx'
$dir = Split-Path $ExcelOut
$FilePathBase = $(Split-Path $ExcelOut -Leaf) -replace '\.xlsx$'
$FilePath = $ExcelOut
$n = 1
while (Test-Path $FilePath) {
$FilePath = Join-Path $dir $($FilePathBase + "-$n" + '.xlsx')
$n++
}
#Saves New File
$Workbook.SaveAs($FilePath, 51)
#Exits Old File
$Excel.Quit()
#Removes Old File
Remove-Item $ResultsFilePath -Force
}

Answer 1

You're opening the CSV as a new workbook, so you just need to open the workbook to which you want to add it as well and move/copy the sheet.
...
$Workbook = $Excel.workbooks.open($ResultsFilePath)
...
$wb2 = $Excel.Workbooks.Open('C:\path\to\other.xlsx')
$Workbook.Sheets.Item(1).Name = 'whatever' # rename sheet
$Workbook.Sheets.Item(1).Copy($wb2.Sheets.Item(1)) # copy sheet
$Workbook.Close($false) # close CSV without saving
$wb2.Save() # save & close workbook
$wb2.Close()
Of course, if you want to insert multiple CSVs into a workbook you'd open the xlsx file just once and save/close it after all sheets were inserted.
If you want to insert sheets from a CSV after a particular sheet in the destination workbook change the Copy() call to something like this:
$Workbook.Sheets.Item(1).Copy([Type]::Missing, $wb2.Sheets.Item(3))