$ie = New-Object -ComObject "InternetExplorer.Application"
$ie.navigate("http://example.local")
while($ie.ReadyState -ne 4) { Start-Sleep -Seconds 5 }
$ie.visible = $true
$doc = $ie.document

$userField = $doc.getElementById("uid")
$passwordField = $doc.getElementById("pwd")
$submitButton = $doc.getElementById("submit")

$userField.value = "userid"
$passwordField.value = "*****"
$submitButton.click()

$shell = New-object -ComObject "Shell.Application"
# The app opens a new window with a timestamp - that's the window I want, so I skip the other window
$ie2 = $shell.Windows() | where {$_.Type -eq "HTML Document" -and $_.LocationName -ne "My App - Parent Window"}
$doc2 = $ie2.document
$frames = @($doc2.getElementsByTagName("FRAME"))
Write-Host $frames.Count # shows "3"
Write-Host $frames[1].Title # shows "Left Nav"

<frameset rows="60,*">
    <frame src="http://example.local/really/long?url" title="Top Nav" name="Top" id="Top">
    <frameset cols="175,*">
        <frame src="http://example.local/left.html" title="Left Nav" name="Left" id="Left">
        <frame src="http://example.local/main.html" title="Main Display" name="Main" id="Main">
    </frameset>
</frameset>