Visual Basic - Un API para cerrar una aplicacion?

Yo se que el ShellExecute llama a una aplicacion pero como hago que esta se cierre desde el Visual Basic?
Gracias por el dato...
Saludos....

Fijate con ésto:

Private Declare Function TerminateProcess Lib "kernel32" (ByVal hProcess As Long, ByVal uExitCode As Long) As Long

Private Declare Function OpenProcess Lib "kernel32" (ByVal dwDesiredAccess As Long, ByVal bInheritHandle As Long, ByVal dwProcessId As Long) As Long
Private Declare Function GetExitCodeProcess Lib "kernel32" (ByVal hProcess As Long, lpExitCode As Long) As Long

public lProcHand As Long

Public Function MyHandle() As Long
Dim lngExecOK As Long
lngExecOK = Shell("c:\windows\calc.exe", vbNormalFocus)
lProcessHandle = OpenProcess(&H100000, True, lngExecOK)
MyHandle = lProcessHandle
End Function

Public Function Terminate(ByVal lPhandle As Long) As Long
Terminate = TerminateProcess(lPhandle, 0)
End Function

si quieres cerrar un applicacion externa, puedes hacer esto.
agarras el handle de la ventana principal, y le mandas un mensaje wm_close, con eso algunas app terminan.