编程，怎么做

Dim isDrawing As Integer
Dim oX As Single, oY As Single

Private Sub Form_Load()
Me.AutoRedraw = True
End Sub

Private Sub Form_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)
If Button = 2 Then
If isDrawing = 0 Then
oX = X: oY = Y
isDrawing = 1
Else
isDrawing = 0
End If
End If
End Sub

Private Sub Form_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)
Dim cirR As Single
If isDrawing = 1 Then
cirR = Sqr((X - oX) ^ 2 + (Y - oY) ^ 2)
Me.Cls
Me.Circle (oX, oY), cirR
End If
End Sub

说明:点下鼠标右键确认圆心开始画圆,再点一下就确定圆的大小.只能画一个圆,想多画自己修该下代码吧