Picturebox用PSet方法画曲线，鼠标移动快，线条就不连贯了，如何解决

Picturebox用PSet方法画曲线，鼠标移动快，线条就不连贯了，怎么解决？

mask是Picturebox控件
Private   Sub   mask_MouseDown(Button   As   Integer,   Shift   As   Integer,   X   As   Single,   Y   As   Single)
md   =   True
End   Sub

Private   Sub   mask_MouseMove(Button   As   Integer,   Shift   As   Integer,   X   As   Single,   Y   As   Single)
'鼠标移动快，线条就不连贯了，怎么解决？
If   md   Then
mask.PSet   (X,   Y)
End   If
End   Sub

Private   Sub   mask_MouseUp(Button   As   Integer,   Shift   As   Integer,   X   As   Single,   Y   As   Single)
md   =   False
End   Sub

------解决方案--------------------
Option Explicit
Dim flag As Boolean, flag2 As Integer, myX As Integer, myY As Integer

Private Sub Picture1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
flag = True: flag2 = 1
myX = X
myY = Y
End Sub

Private Sub Picture1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
If flag Then
If flag2 = 1 Then
flag2 = flag2 + 1
Picture1.Line (myX, myY)-(X, Y), vbGreen
Else
Picture1.Line -(X, Y), vbGreen
End If
End If
End Sub

Private Sub Picture1_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)
flag = False: flag2 = 1

End Sub