How to generate a loop that relies on external command input

Hi Experts,

I wrote a PS script that generate a BITS job to download files from a remote server using BITSAdmin command line.
The script works fine.

I need to add a section at the end of the script to loop a state check for the BITS Job and run BITSAdmin /complete <JOB> after all files where downloaded.

I though of using BITSAdmin /GETSTATE <JOB> that shows the job progress
The general logic is:

[string]$LogArchiveState = BITSAdmin /GETSTATE logArchiveDaily
if ($LogArchiveState.Contains("TRANSFERRED")) {BITSAdmin /COMPLETE logArchiveDaily;EXIT}

I need these two lines to run every 30 minutes. (Start-Sleep -s 1800 ?)
Any idea how can I get this to work with a WHILE / DO WHILE loop?
Other alternative?

Thanks.

P.S. I am using Windows 2003 Server, this is why I can not use the BITS built in cmdlets (which requires BITS engine 4.0 :-(