[5分]倒数第二行：SendKeys ("{Tab}")什么意思？

还有个问题，组合框输入字符后，自动下拉相符值。请问：如果NoInList事件中SendKeys ("{Tab}")是什么意思？
Private Sub 客户编码_KeyDown(KeyCode As Integer, Shift As Integer)
    Select Case KeyCode
    Case vbKeyUp, vbKeyDown
        Me.客户编码.OnChange = ""
    Case Else
        Me.客户编码.OnChange = "[Event Procedure]"
    End Select
End Sub

Private Sub 客户编码_KeyUp(KeyCode As Integer, Shift As Integer)
    Dim a As String
    a = "*" & Me.客户编码.Text & "*"
    Me.客户编码.RowSource = "SELECT tbl_Customer.客户编码, tbl_Customer.客户名称 FROM tbl_Customer Where 客户名称 like '" & a & "';"
    Me.客户编码.Dropdown
    b = Me.客户编码.Column(0, 0)
End Sub

Private Sub 客户编码_NotInList(NewData As String, Response As Integer)
    Dim Ctl As Control
    Set Ctl = Me!客户编码
    Response = acDataErrContinue
    Ctl.Undo
    Me.客户编码 = b
    Me.客户编码.RowSource = "SELECT tbl_Customer.客户编码, tbl_Customer.客户名称 FROM tbl_Customer;"
    SendKeys ("{Tab}")
End Sub

	 这个也是几个月前写的，现在又不懂了。。。
惭愧