Variable is an empty string even after writing the string to host - powershell

Question

I'm trying to build a little app to help admins swap powerapps ownership around in PowerShell. I'm sure this is me misunderstanding how scopes work in PowerShell but I'm stumped and need a little help.
The app is pretty simple, it queries the PowerApp environment for a list of apps, their owners, and their GUIDs and presents them in a datagridview. Users select the app they're going to change, click a button, put an email address in, and then click another button. On that click, the app grabs the user's GUID from AAD and then runs a command to flip ownership of the app to that user's GUID.
But for some reason, the second function keeps reporting that the GUID and App Name I collected in the first screen are empty strings.
Here's the whole thing (minus credential info, natch):
#Get Apps on environment
$apps = Get-AdminPowerApp -EnvironmentName $powerAppEnv
#Form Details
$ChangePowerAppOwnership = New-Object system.Windows.Forms.Form
$ChangePowerAppOwnership.ClientSize = New-Object System.Drawing.Point(500,300)
$ChangePowerAppOwnership.text = "Change PowerApp Ownership"
$ChangePowerAppOwnership.TopMost = $false
$appsLabel = New-Object system.Windows.Forms.Label
$appsLabel.text = "Available Apps"
$appsLabel.AutoSize = $true
$appsLabel.width = 25
$appsLabel.height = 10
$appsLabel.location = New-Object System.Drawing.Point(15,20)
$appsLabel.Font = New-Object System.Drawing.Font('Segoe UI',10)
$availableApps = New-Object system.Windows.Forms.DataGridView
$availableApps.width = 470
$availableApps.height = 200
$availableApps.location = New-Object System.Drawing.Point(15,40)
$availableApps.MultiSelect = $false
$availableApps.SelectionMode = "FullRowSelect"
$availableApps.ColumnCount = 3
$availableApps.ColumnHeadersVisible = $true
$availableApps.Columns[0].Name = "App Name"
$availableApps.Columns[1].Name = "Current Owner"
$availableApps.Columns[2].Name = "GUID"
foreach($app in $apps){
$availableApps.Rows.Add(#($app.DisplayName,($app.Owner | Select-Object -Expand displayName),$app.AppName))
}
$promptForAdmin = New-Object system.Windows.Forms.Button
$promptForAdmin.text = "Next"
$promptForAdmin.width = 60
$promptForAdmin.height = 30
$promptForAdmin.location = New-Object System.Drawing.Point(424,260)
$promptForAdmin.Font = New-Object System.Drawing.Font('Segoe UI',10)
$promptForAdmin.Add_Click({ GetNewAdmin $availableApps.SelectedRows})
$adminLabel = New-Object system.Windows.Forms.Label
$adminLabel.text = "New Administrator"
$adminLabel.AutoSize = $true
$adminLabel.width = 25
$adminLabel.height = 10
$adminLabel.location = New-Object System.Drawing.Point(14,13)
$adminLabel.Font = New-Object System.Drawing.Font('Segoe UI',10)
$adminEmailField = New-Object system.Windows.Forms.TextBox
$adminEmailField.multiline = $false
$adminEmailField.width = 200
$adminEmailField.height = 20
$adminEmailField.location = New-Object System.Drawing.Point(135,12)
$adminEmailField.Font = New-Object System.Drawing.Font('Segoe UI',10)
$changeAppAdmin = New-Object system.Windows.Forms.Button
$changeAppAdmin.text = "Go"
$changeAppAdmin.width = 60
$changeAppAdmin.height = 30
$changeAppAdmin.location = New-Object System.Drawing.Point(424,260)
$changeAppAdmin.Font = New-Object System.Drawing.Font('Segoe UI',10)
$ChangePowerAppOwnership.controls.AddRange(#($appsLabel,$availableApps,$promptForAdmin))
$ChangePowerAppOwnership.ShowDialog()
function GetNewAdmin {
param($selectedRows)
$selectedAppGuid = $selectedRows | ForEach-Object{ $_.Cells[2].Value }
$selectedAppName = $selectedRows | ForEach-Object{ $_.Cells[0].Value }
Write-Host "Selected App GUID: $selectedAppGuid" #this and the following command show values
Write-Host "Selected App Name: $selectedAppName"
$appsLabel.Visible = $false
$availableApps.Visible = $false
$promptForAdmin.Visible = $false
$changeAppAdmin.Add_Click( { AssignNewAdmin $selectedAppGuid $selectedAppName $adminEmailField.Text} )
$ChangePowerAppOwnership.controls.AddRange(#($adminLabel,$adminEmailField,$changeAppAdmin))
}
function AssignNewAdmin {
param(
$selectedAppGuid,
$selectedAppName,
$newAdminEmail
)
Write-Host "AppID: $selectedAppGuid" #this is always empty
Connect-AzureAD -Credential $credentials
$user = Get-AzureADUser -ObjectId $newAdminEmail
$newAppOwnerGuid = $user | select ObjectId
$newAppOwnerName = $user | select DisplayName
$msgBoxMessage = "Are you sure you want to grant ownership of $selectedAppName to $newAppOwnerName`?"
$msgBoxInput = [System.Windows.Forms.MessageBox]::Show($msgBoxMessage,"Confirm","YesNo","Error")
switch ($msgBoxInput){
'Yes'{
Set-AdminPowerAppOwner -AppName $selectedAppGuid -EnvironmentName $powerAppEnv -AppOwner $newAppOwnerGuid
# try{
# $ChangePowerAppOwnership.Close()
# }
# catch{
# Write-Host "Could not update this app's administrator role."
# }
}
'No' {
$ChangePowerAppOwnership.Close()
}
}
}

Answer 1

Move the functions to the top or at least higher than $ChangePowerAppOwnership.ShowDialog() or the script wont find them(the execution stops till you close the Form...).
The same goes for the function AssignNewAdmin as it is used in GetNewAdmin but defined later.

Answer 2

Courtesy of Jeroen Mostert's comment, adding GetNewClosure to my second Add_Click function did the trick.