EXCEL制作单位自动换算，期盼高手解答！

Question

例如：米，分米，厘米，毫米 的换算。当在米下输入1时自动在 分米 厘米 毫米下出现相应的值，当在分米下输入1时自动在 米 厘米 毫米下出现相应的值（必须在一个表中，就像网页上那种单位换算，不管输入哪个都会自动换算），希望高手能详细讲解，问题解决另追加高分!谢谢！

Answer 1

'假设A1～D1分别为米、分米、厘米、毫米，需要换算的单元格位置分别是A2、B2、C2、D2
'按Alt+F11打开脚本编辑，点击左侧工作表名称，然后在右侧窗口粘贴如下代码：
Private Sub Worksheet_SelectionChange(ByVal Target As Range): On Error Resume Next
If Target.Count = 1 And Target.Column = 1 And Cells(2, 1) <> 0 Then Cells(2, 2) = Cells(2, 1) * 10: Cells(2, 3) = Cells(2, 1) * 100: Cells(2, 4) = Cells(2, 1) * 1000
If Target.Count = 1 And Target.Column = 2 And Cells(2, 2) <> 0 Then Cells(2, 1) = Cells(2, 2) * 0.1: Cells(2, 3) = Cells(2, 2) * 10: Cells(2, 4) = Cells(2, 2) * 100
If Target.Count = 1 And Target.Column = 3 And Cells(2, 3) <> 0 Then Cells(2, 1) = Cells(2, 3) * 0.01: Cells(2, 2) = Cells(2, 3) * 0.1: Cells(2, 4) = Cells(2, 3) * 10
If Target.Count = 1 And Target.Column = 4 And Cells(2, 4) <> 0 Then Cells(2, 1) = Cells(2, 4) * 0.001: Cells(2, 2) = Cells(2, 4) * 0.01: Cells(2, 3) = Cells(2, 4) * 0.1
If Cells(2, 2) <> "" And Application.IsNumber(Cells(2, 2)) = False Then Range("A2:D2").ClearContents: MsgBox " 你所输入的不是有效数字，请重新输入！ "
End Sub
'说明：输入数字敲回车键或者点击鼠标后，光标所停放的单元格应该在当前列中

Answer 2

需要用到VBA了