Findong if a winow is open

Hi, basically, I need to know, how I can check if a window is open, and if it is do something.

The window is in another program :)

Use the FindWindowEx function.

VB Code:

Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal hWnd1 As Long, ByVal hWnd2 As Long, ByVal lpsz1 As String, ByVal lpsz2 As String) As Long
 
Private Sub Command1_Click()
    Dim hApp as Long
    hApp = FindWindowEx(0, 0, "ClassName", "WindowName")
    If hApp <> 0 Then MsgBox "Window is open
End Sub