You can try WSH SendKeys method. For the list of keys see http://msdn.microsoft.com/library/default.asp?url=/library/en-us/script56/html/wsmthsendkeys.asp.

oWSH = CreateObject( "WScript.Shell" )
WSH.SendKeys(...)

>I'm trying to capture data on webpage automatically via a program. When I open the webpage in IE, a dialog box pops up for entering username and password. The dialog box is not part of an html page. How can I automate entering my username and password by code?
>
>TIA