vb中怎样使窗口中的image图片不断闪烁？

vb中怎样使窗口中的image图片来回不停闪烁？
怎样才能将密码口令设成可修改模式?
比如：1.登陆-请输入口令...
2.登陆完成后，修改密码：（1）请输入原密码
（2）请输入新密码
（3）请再次输入新密码
3.修改密码成功

Private Sub Command1_Click()

Dim b As String

If Dir("c:\paw.db") = "" Then
Open "c:\paw.db" For Output As #1
Print #1, Text1.Text
Close #1

Else

Open "c:\paw.db" For Input As #1
Line Input #1, b
Close #1

If Text1.Text <> b Then
MsgBox "密码错误! 请重新输入", 48, "提示"
Exit Sub
End If

End If

Text1.Text = "请输入旧密码"
Text2.Visible = True
Text3.Visible = True
Command2.Visible = True
Command1.Visible = False
End Sub

Private Sub Command2_Click()
Dim b As String
Open "c:\paw.db" For Input As #1
Line Input #1, b
Close #1
If Text1.Text <> b Then
MsgBox "旧密码错误"
Exit Sub
End If
If Text2.Text = Text3.Text Then