non serve impostare timer vari

basta cambiare metodo per il tracciamento della linea.

usa 2 eventi: MouseDown e MouseMove

codice:
Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
Me.PSet (X, Y)
End Sub

Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
Me.Line -(X, Y)
End Sub
così dovrebbe andare

Boolean