Private oldX As Single
Private oldY As Single
Private StartX As Single
Private StartY As Single
 
Private Sub Form_Load()
    Timer1.Interval = 100
    Me.DrawStyle = vbDashDotDot ' oder vbDot oder vbDash oder vbDashDot
End Sub
 
Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
    Timer1.Enabled = False
    StartX = X
    StartY = Y
    oldX = StartX
    oldY = StartY
    Me.Cls
End Sub
 
Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
    Dim sm As Integer
    If Button = 1 Then
        sm = Me.DrawMode
        Me.DrawMode = vbInvert
        Me.Line (StartX, StartY)-(oldX, oldY), , B
        Me.Line (StartX, StartY)-(X, Y), , B
        oldX = X
        oldY = Y
        Me.DrawMode = sm
    End If
End Sub
 
Private Sub Form_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
    Timer1.Enabled = True
End Sub
 
Private Sub Timer1_Timer()
    Dim saveddrawstyle As Integer
    Dim savedmodus As Integer
    saveddrawstyle = Me.DrawStyle
    savedmodus = Me.DrawMode
    Me.DrawStyle = vbSolid
    Me.DrawMode = vbInvert
    Me.Line (StartX, StartY)-(oldX, oldY), , B
    Me.DrawMode = savedmodus
    Me.DrawStyle = saveddrawstyle
End Sub