How Do You Undo Macros In VB? Is It Actually Possible?

Add this code to any macro you want to be able to undo
Sum Example()
Call SaveUndo
Application.OnUndo "Undo_Macro", "Undo_Macro" (put this at end of macro)
End Sub

Add this to the declarations at the top of the same module:
Public workbooknumber As Integer
Public currentworkbook As String
Public newworkbook As String

Then add the following two subs to complete the job:
Sub SaveUndo()
Dim Number As String

If ActiveWorkbook.Path = "C:\TEMP" Then workbooknumber = workbooknumber + 1

If workbooknumber = 0 Then Number = "" Else Number = workbooknumber

currentworkbook = ActiveWorkbook.Name

newworkbook = Replace(currentworkbook, ".xls", "")
newworkbook = newworkbook + Number
newworkbook = newworkbook + ".xls"

SAVE:

ActiveWorkbook.SaveCopyAs "C:\TEMP\" + newworkbook

End Sub

Sub Undo_Macro()

Workbooks(currentworkbook).Close SaveChanges:=False

Workbooks.Open ("C:\TEMP\" + newworkbook)

MsgBox ("Make sure you save this file to the correct directory. " + newworkbook + " is currently saved in the temp directory")

End Sub

The above two macros temporarily save your file before running the desired macro. After running the original macro, select undo_macro on the undo button list and you will be reverted back to the saved version of the file.

Hope this helps!