出现异常后，程序还能回到误操作之前的状态

出现错误后，程序还能回到误操作之前的状态
这段代码是控制TEXT1中只允许输入数字和小数点的：
Private Sub Text1_KeyPress(KeyAscii As Integer)
If mf1.Col = 6 Or mf1.Col = 7 Or mf1.Col = 8 Then ‘mf1是MSFlexGrid
If (KeyAscii > 57 Or KeyAscii < 48) And KeyAscii <> 46 And KeyAscii <> 8 Then KeyAscii = 0
End If
End Sub
但有时误操作，输入两个小数点就不行了，怎样让其只能输入一个小数点，也像这样第二个小数点想字母一样根本就输不进去。
VB的程序一旦那里误操作出现错误就直接崩溃，只能将整个程序“结束”。能不能出现错误后，程序还能回到误操作之前的状态！

[解决办法]
http://blog.csdn.net/supermanking/article/details/2959044

http://blog.csdn.net/supermanking/article/details/2799053



[解决办法]

VB code

Private Sub Text1_KeyPress(KeyAscii As Integer)    If mf1.Col = 6 Or mf1.Col = 7 Or mf1.Col = 8 Then 'mf1是MSFlexGrid        '    If (KeyAscii > 57 Or KeyAscii < 48) And KeyAscii <> 46 And KeyAscii <> 8 Then KeyAscii = 0        Select Case KeyAscii        Case 8 '跳过 值为8        Case 46            If InStr(Text1, ".") > 0 Then                KeyAscii = 0            End If        Case Is < 48            KeyAscii = 0        Case Is > 57            KeyAscii = 0        End Select    End IfEnd Sub
[解决办法]
用 On error Resume Next 然后用 If not Err.Number then 判断是否发生错误，用 Err.Clear 清楚错误