有意思。
能不能把你已经写了的代码给我看看？那怕只有一行。

免费提供一行代码

dim b as long
...
if b = 0 then
msgbox"除数不能为0!"
end if 

是对话框弹出.自己研究研究怎么显示到3里面.

建议以后象这种帖子直接删除，VB的名声就是被这些人搞坏的

        数据输入：a            数据输入：b            结果 （a*b or a/b ）

          运行                   清除                结束
        command1               command2            command3

            O                      O
           乘法                   除法 

---------------------------------------------------------------------------------------------
            Private Sub Command1_Click()
               show
               Dim a As Single,b As Single
               a=Val(Text1.Text)
               b=Val(Text2.Text)
               if text2.text=0 then text3.text="除数不能为0"              
               if Option1=True Then Text3.Txxt=a*b
               if Option2=True Then Text3.Text=a/b
               Text1.SetFocus
            End Sub

            Private Sub Command2_Click()
               Text1.Text="   "
               Text2.Text="   "
               Text3.Text="   "
            End Sub

            Privte Sub Command3_Click()
                End
            End Sub

            Privat Sub Option1_Click()
               Option1.Value=True
            End Sub

            Private Sub Option_Click()
               Option2.Value=True
            End Sub
         供参考