Option Explicit
Private Declare Function SetCapture Lib "user32" (ByVal hwnd As Long) As Long
Private Declare Function ReleaseCapture Lib "user32" () As Long
Private Declare Function GetCapture Lib "user32" () As Long
Private Sub Command1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
With Command1
If (X < 0) Or (Y < 0) Or (X > .Width) Or (Y > .Height) Then 'MouseLeave
Call ReleaseCapture
ElseIf GetCapture() <> .hwnd Then 'MouseEnter
Call SetCapture(.hwnd)
Else
'Normal MouseMove
End If
End With
End Sub