Private Declare Function GetCursorPos Lib "user32" _
  (lpPoint As POINTAPI) As Long
 
Private Declare Function ClientToScreen Lib "user32" _
  (ByVal hwnd As Long, lpPoint As POINTAPI) As Long
 
Private Type POINTAPI
  X As Long
  Y As Long
End Type
 
Dim P1 As POINTAPI
Dim P2 As POINTAPI
 
Private Sub Form_Load()
  Timer1.Enabled = False
  Timer1.Interval = 50
End Sub
 
Private Sub Timer1_Timer()
  Dim Result&, CurPos As POINTAPI
 
  Result = GetCursorPos(CurPos)
 
  If CurPos.X < P1.X Or CurPos.X > P2.X Or _
    CurPos.Y < P1.Y Or CurPos.Y > P2.Y Then
    Timer1.Enabled = False
    Command1.Caption = "out"
  End If
End Sub
 
Private Sub Command1_MouseMove(Button As Integer, Shift As Integer, X As _
  Single, Y As Single)
  Dim Result&
 
  If Timer1.Enabled = False Then
    P1.X = ScaleX(Command1.Left, ScaleMode, vbPixels)
    P1.Y = ScaleY(Command1.Top, ScaleMode, vbPixels)
    Result = ClientToScreen(hwnd, P1)
 
    P2.X = ScaleX(Command1.Left + Command1.Width, ScaleMode, vbPixels)
    P2.Y = ScaleY(Command1.Top + Command1.Height, ScaleMode, vbPixels)
    Result = ClientToScreen(hwnd, P2)
 
    Timer1.Enabled = True
    Command1.Caption = "in"
  End If
End Sub

Gruß
Marcus