If you open an AutoCAD file in notepad, the first six characters contain a code that correlates to the AutoCAD version.
Here are the codes and corresponding versions.
AC1027 AutoCAD 2013
AC1024 AutoCAD 2010/2011/2012
AC1021 AutoCAD 2007/2008/2009
AC1018 AutoCAD 2004/2005/2006
AC1015 AutoCAD 2000/2000i/2002
AC1014 Release 14
AC1012 Release 13
AC1009 Release 11/12
AC1006 Release 10
AC1004 Release 9
AC1003 Version 2.60
AC1002 Version 2.50
AC1001 Version 2.22
AC2.22 Version 2.22
AC2.21 Version 2.21
AC2.10 Version 2.10
AC1.50 Version 2.05
AC1.40 Version 1.40
AC1.2 Version 1.2
MC0.0 Version 1.0
As new releases become available, new codes will probably be added. I'm not sure how files that were created with products other than AutoCAD show up, so you'll have to look into that.
Here's a simple excel VBA function that could be used to extract the first 6 characters of any text file. Put it in a module, and it should be available to you in any cell.
Code:
Public Function GetAcadVersion(ByVal FileName As String) As String
Dim TextLine As String
Open FileName For Input As #1 ' Open file.
Line Input #1, TextLine ' Read line into variable.
GetAcadVersion = Left(TextLine, 6)
Close #1 ' Close file.
End Function
AcadVersionFromFileExample.xls
I also attached a sample excel file to get you started.