Look at the "if-then" statement I've inserted within your code. You can use either the title or url to identify the child and set focus on it. Once it has focus, you can get the elements of the child window.
Set objShell = CreateObject("Shell.Application")
IE_count = objShell.Windows.Count
For x = 0 To (IE_count - 1)
On Error Resume Next ' sometimes more web pages are counted than are open
my_url = objShell.Windows(x).Document.Location
my_title = objShell.Windows(x).Document.Title
If my_title Like "Something that identifies your child window" Then
Set ie = objShell.Windows(x)
Exit For
Else
End If
Next