PowerShell to insert code in Excel VBA

I'm creating a script for my Work, where i need to insert some VBA code in Excel. I've all worked out, except how to insert the code in the VBProject. I need 2 codes inserted. I need a code inserted in Sheet1(aka tmpArk1) and in ThisWorkbook. How do i do this?

My code so far:

Function Get-FileName($initialDirectory)
{
[System.Reflection.Assembly]::LoadWithPartialName("System.windows.forms") |   Out-Null

$OpenFileDialog = New-Object System.Windows.Forms.OpenFileDialog
$OpenFileDialog.initialDirectory = $initialDirectory
$OpenFileDialog.filter = "xlsx (*.xlsx)| *.xlsx"
$OpenFileDialog.ShowDialog() | Out-Null
$OpenFileDialog.filename
}

$inputplace = Get-FileName "P:\" ".xlsx"
$inputname = [System.IO.Path]::GetFileNameWithoutExtension($inputplace)
$inputpath = [System.IO.Path]::GetDirectoryName($inputplace)

########################################
########### Starting Excel #############
########################################


$Excel = New-Object -ComObject Excel.Application
$ExcelVersion = $Excel.Version

New-ItemProperty -Path "HKCU:\Software\Microsoft\Office\$ExcelVersion\Excel\Security" -Name AccessVBOM -Value 1 -Force | Out-Null 
New-ItemProperty -Path "HKCU:\Software\Microsoft\Office\$ExcelVersion\Excel\Security" -Name VBAWarnings  -Value 1 -Force | Out-Null

$Excel.Visible = $true
$Excel.DisplayAlerts = $false

########################################
####### Working with workbook ##########
########################################

#Opens workbook to be transfered from, ReadOnly
$workbook1 = $Excel.Workbooks.Open($inputplace,$null, $true)

#Create workbook to work with
$workbook2 = $Excel.Workbooks.add()


########################################
####### The code to be inserted ########
########################################

#Code Alpha

#$codeAlfa = @"
#    Some code here
#"@

#Code beta

#$codeBeta = @"
#    Some code here
#"@


########################################
####### Working with worksheets ########
########################################

#Add 1 worksheets to workbook
$workbook2.Worksheets.Add()

#Transfer Sheet from opened workbook to new workbook
$SheetToCopy = $workbook1.sheets.item(1)
$TransferTarget = $workbook2.sheets.item(1)
$SheetToCopy.copy($TransferTarget)

#Change name of all 4 worksheets
$workbook2.Worksheets.Item(1).name = "tmpArk1"
$workbook2.Worksheets.Item(2).name = "output"
$workbook2.Worksheets.Item(3).name = "net"
$workbook2.Worksheets.Item(4).name = "data"
$workbook2.Worksheets.Item(5).name = "bilag"

#Close Workbook1
$Workbook1.Close()

#inserting the codes
$ExcelModuleAlfa = $workbook2.VBProject.VBComponents.Add(1)
$ExcelModuleAlfa.CodeModule.AddFromString($codeAlfa)

########################################
######### Clean up enviroment ##########
########################################

#Save workbook to hard drive
Add-Type -AssemblyName Microsoft.Office.Interop.Excel
$workbook2.SaveAs("P:\" + $inputname + "_auto",[Microsoft.Office.Interop.Excel.XlFileFormat]::xlExcel8)

#Close workbook and quit Excel
#$Excel.Workbooks.Close()
#$Excel.Quit()

#Stop Excel process
#Get-Process excel | Stop-Process -Force

#Release com object
[System.Runtime.Interopservices.Marshal]::ReleaseComObject($Excel)

When I try to run the script, I get this as my output error.

You cannot call a method on a null-valued expression.
At C:\Users\G017116\Desktop\PowerShell InWork.ps1:995 char:57
+ $ExcelModuleAlfa = $workbook2.VBProject.VBComponents.Add <<<< (1)
+ CategoryInfo          : InvalidOperation: (Add:String) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull

You cannot call a method on a null-valued expression.
At C:\Users\G017116\Desktop\PowerShell InWork.ps1:996 char:42
+ $ExcelModuleAlfa.CodeModule.AddFromString <<<< ($codeAlfa)
+ CategoryInfo          : InvalidOperation: (AddFromString:String) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull