Autoamting Internet Explorer webpage using VBA, but stuck with a window popup to enter a value

[SATZ]

Automating the manual process in Internet explorer webpage using VBA. When clicking on a text box in a page, it displays a seperate Window Popup.

There is a text field in the window popup, where i have to enter a value, but no HTML code is associated to that popup(as i dont see Inspect element to get the HTML code).

So how do i get to the textbox in the window dialog box that pops up and enter the value?? when there is no "inspect element" is available.

Note: Webpage is access restricted,so cant share the link.

**************************Code*****************************************
On Error GoTo ErrHandler
Application.ScreenUpdating = False

Set data_sheet = ThisWorkbook.Sheets("Input")

' Count the number of rows
iTotalRows = data_sheet.Cells(Rows.Count, 1).End(xlUp).Row

'If iTotalRows > 1 Then
' Start session
Dim ie As InternetExplorer
Dim win As Object
Dim elements As MSHTML.IHTMLElementCollection
Dim nameValueInput As MSHTML.HTMLInputElement
Dim oHTML_Element As IHTMLElement
Dim Outcome
Dim i As Long

Dim Wnk As HTMLLinkElement

Set ie = New InternetExplorerMedium
ie.Silent = True

ie.Navigate "URL"

ie.Visible = True

Do While ie.readyState <> READYSTATE_COMPLETE

Loop

Dim idoc As MSHTML.HTMLDocument
Set idoc = ie.Document

Do While ie.Busy = True Or ie.readyState < 4: DoEvents: Loop

Application.Wait (Now() + TimeValue("00:00:2"))

Set elements = idoc.getElementsByName("userBSB")

For Each oHTML_Element In idoc.getElementsByTagName("input")
If oHTML_Element.Name = "userBSB" Then oHTML_Element.Click: Exit For
Next

Do While ie.Busy = True Or ie.readyState < 4: DoEvents: Loop
Application.Wait (Now() + TimeValue("00:00:3"))


' Not sure how to proceed from here to give a value in the text box of a new window popup,couldnt get a HTML code to it(F12, or Inspect element is anot available)

Could anyone let me know how do i proceed from here?
Any help would be appreciated.