Try the following code. Of course, you'll want to change the variable values to match your testing needs. Also, if you don't want to use the local computer for the domain, you'll need to change that too. If not, it retrieves the computer name for the domain automatically:
set objShell= Wscript.CreateObject(''WScript.Shell'')
Set objNetwork = WScript.CreateObject(''WScript.Network'')
''Variable Values assignment
domain = objNetwork.ComputerName
program = ''iexplore.exe''
domainUser = ''Testuser1''
password = ''passwordvalue''
objShell.Run ''runas /env /user:'' & domain & '''' & domainUser & '' '' & ''''''C:Program FilesInternet Exploreriexplore.exe''''''
Wscript.Sleep 2000
'Delay before typing password in window. Adjust if needed
objShell.Sendkeys password
Wscript.Sleep 1000
objShell.SendKeys ''{ENTER}''
Wscript.Quit