怎么限制文本框的数据格式？

[vfp_system]

怎么限制文本框的数据格式？例如：我要用户在文本框当中只能按下面的格式输入，
四位数代表年，二位代表月，二位代表日，三者之间用点隔开，但这个点要显示在文本框当中，而且不能删除或改变。

[goodname008]

使用VB6企业版中的MaskEdBox控件，将其Mask属性设为####.##.##

[rainstormmaster]

textbox的实现方法,建议使用MaskEdBox:

Private Sub Form_Load()
Text1.Text = ""
End Sub

Private Sub Text1_KeyPress(KeyAscii As Integer)
Dim s As String
s = Text1.Text
Dim i As Long
i = Len(s)
If i >= Len("####.##.##") Then
KeyAscii = 0
Exit Sub
Else
If KeyAscii <> 8 Then '如果按下的不是退格键
Select Case i
Case 0
If KeyAscii < 48 Or KeyAscii > 57 Then
KeyAscii = 0
Exit Sub
End If
Case 1
If KeyAscii < 48 Or KeyAscii > 57 Then
KeyAscii = 0
Exit Sub
End If
Case 2
If KeyAscii < 48 Or KeyAscii > 57 Then
KeyAscii = 0
Exit Sub
End If
Case 3
If KeyAscii < 48 Or KeyAscii > 57 Then
KeyAscii = 0
Exit Sub
End If
Case 4
If KeyAscii <> 46 Then
KeyAscii = 0
Exit Sub
End If
Case 5
If KeyAscii < 48 Or KeyAscii > 57 Then
KeyAscii = 0
Exit Sub
End If
Case 6
If KeyAscii < 48 Or KeyAscii > 57 Then
KeyAscii = 0
Exit Sub
End If
Case 7
If KeyAscii <> 46 Then
KeyAscii = 0
Exit Sub
End If
Case 8
If KeyAscii < 48 Or KeyAscii > 57 Then
KeyAscii = 0
Exit Sub
End If
Case 9
If KeyAscii < 48 Or KeyAscii > 57 Then
KeyAscii = 0
Exit Sub
End If
End Select
End If
End If
End Sub