The first thing you need to know is the process name you can find out by opening Task Manager . For example use "chrome.exe" to close chrome , etc
Sub sample_1()
' process u want to terminate
Call TerminateProcess("googletalk.exe")
End Sub
Private Sub TerminateProcess(ByVal app_exe As String)
Dim Process As Object
For Each Process In GetObject("winmgmts:").ExecQuery("Select Name from Win32_Process Where Name = '" & app_exe & "'")
Process.Terminate
Next Process
End Sub