function doit {
    Get-Content -path "C:\xy.bat" | Out-File "C:\new.txt" -Force
    $bat_n = "C:\new.txt"
    $bat_f = New-Item "C:\new.bat" -Force
    $userid = $txtbox_userid.Text
    $ticketname = $txtbox_ticketname.Text
    $time = $txtbox_time.Text
    (Get-Content $bat_n) | Foreach-Object {
        $_ -replace 'xy', "$userid" `
            -replace 'update', "$ticketname" `
            -replace '"7","00"', '"8","00"' `
    } | Set-Content $bat_f
}

[void]$global:form_main.ShowDialog()
$btn_doit.Add_Click( { doit })