$progress = 0
while([math]::Round($progress) -lt 100) { # use any loop you like
$progress = $progress + ((100 - $progress) / 10) # the bigger the last integer, the slower the progress bar completes
Write-Progress -Activity 'Progress' -Status "Waiting" -PercentComplete $progress
Start-Sleep 1 # do something useful here, make it count
}
Write-Progress -Activity 'Progress' -Completed
start-sleep 2