Hide progress of Invoke-WebRequest

How can I hide the progress display of Invoke-WebRequest? I do a lot of successive requests and have my own Write-Progress display that I use, so I don't need the built-in one popping up underneath it every time.

I use the mshtml results (the IE COM object) that are created from the result of Invoke-WebRequest automatically, so I can't switch to a WebClient or something like that, unless someone provides instructions on how to get an mshtml object from a WebClient request.

Use the $progressPreference variable. It should have a value of 'Continue' by default unless you've edited it elsewhere, which tells Powershell to display the progress bar. Since you mentioned that you have your own custom progress displays, I would reset it immediately after the cmdlet is executed. For example:

$progressPreference = 'silentlyContinue'    # Subsequent calls do not display UI.
Invoke-WebRequest ...
$progressPreference = 'Continue'            # Subsequent calls do display UI.
Write-Progress ...

More info on preference variables at about_preference_variables. Here's the entry for $ProgressPreference:

$ProgressPreference
-------------------
Determines how Windows PowerShell responds to progress updates 
        generated by a script, cmdlet or provider, such as the progress bars
        generated by the Write-Progress cmdlet. The Write-Progress cmdlet 
        creates progress bars that depict the status of a command.

        Valid values:
          Stop:               Does not display the progress bar. Instead,
                                it displays an error message and stops executing.

          Inquire:            Does not display the progress bar. Prompts
                                for permission to continue. If you reply
                                with Y or A, it displays the progress bar.

          Continue:           Displays the progress bar and continues with
          (Default)             execution.

          SilentlyContinue:   Executes the command, but does not display
                                the progress bar.