Simple Visual Basic Program

Is it a specific window you are trying to close? If you know the windows caption it can be done using the FindWindow API:

' add a timer and set the interval to 1000
Private Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Sub Sleep Lib "kernel32" (ByVal milliseconds As Long)
Private Const WM_CLOSE = &H10

Private Sub Timer1_Timer()
' where "Untitled - Notepad" is the window caption
CloseProgram ("Untitled - Notepad")
End Sub

Private Sub CloseProgram(ByVal Caption As String)
Dim Handle
Handle = FindWindow(vbNullString, Caption)
If Handle = 0 Then Exit Sub
' wait 5 secs
Sleep 5000
SendMessage Handle, WM_CLOSE, 0&, 0&
End Sub