I am creating a screensaver that has a pictured displayed and then I have a black line drawn across 10 pixels wide that scrolls across and then down and across again. The result is a black screen. I then want to erase the live in the same fashion revealing the picture underneath. I can create the line but can not erase the line. I can create a new line and have a white screen but I want to erase. Any suggestions? Here is the code so far

Private Sub Timer1_Timer()
n = n + 1
If n > 1 Then
Line (1, 1)-(n, M), vbBlack, BF
DrawWidth = 10
n = n + 1
M = M + 1
End If
If n > 1001 Then
M = M + 10
n = 1
End If
End Sub