try like this
Code:
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" _
    (ByVal lpClassName As String, ByVal lpWindowName As String) As Long

Private Declare Function ShowWindow Lib "user32" (ByVal hwnd As Long, _
    ByVal nCmdShow As Long) As Long

Private Declare Function SetForegroundWindow Lib "user32.dll" (ByVal hwnd As Long) As Long

Private Const SW_SHOWNORMAL = 1
Private Const SW_SHOWMINIMIZED = 2
Private Const SW_SHOWMAXIMIZED = 3

Private Sub Command1_Click()
Dim lHwnd As Long
lHwnd = FindWindow("Notepad", vbNullString)
If lHwnd <> 0 Then
    MsgBox "Notepad is opened!", vbInformation, "Notepad"
    ShowWindow lHwnd, 1
    SetForegroundWindow (lHwnd)
Else
    MsgBox "Notepad isn't opened", vbInformation, "Window not found."
End If
End Sub