第一组的作用禁止在文本框中输入数值
Private Sub Text1_KeyPress(KeyAscii As Integer)
   Char = Chr(KeyAscii)
    If IsNumeric(Char) Then                           第一组运行正常
        KeyAscii = Char
    End If
End Su

第二组是在第一组的基础上引伸
Private Sub Text1_KeyPress(KeyAscii As Integer)
Char = Chr(KeyAscii)
 If IsNumeric(Char) Then
  KeyAscii = Char
'  Else                                               加注释部分是我另外加的引伸运行不正常
'   Not IsNumeric(Char)
'  MsgBox "请输入数字", vbExclamation, "提示信息"
'  Text1.Text = ""
   End If
End Sub

我的理解:
     keyascii-键码常数     Chr(keyascii)-转变成数值字符串

  求助:如何能达到我要求的效果      
                                                                                             谢谢

if KeyAscii >=vbkey0 and KeyAscii <=vbkey9 then
endif

您的代码不怎么明白
    谢谢您的回复

KeyAscii = Char       'char是个字符变量 KeyAscii是个Integer整形变量  
                       就相当于 KeyAscii = Val(Char)  而CHAR不是数字字符  KeyAscii的结果只能是0
                       所以这句等同于:KeyAscii =0     效果就是屏蔽该KeyAscii码值的按键.   

Not IsNumeric(Char) 是一个表达式 ,而不是一个完整的执行语句.把它单独写一行是不正确的.
 
'''''''''''''''''''''''''''''''''''''''''
Private Sub Text1_KeyPress(KeyAscii As Integer)
If Not IsNumeric(Chr(KeyAscii)) Then           
   KeyAscii = 0                                          
   MsgBox "请输入数字", vbExclamation, "提示信息"
End If
End Sub