Tim, yes they work, I had to revise the reg code to the following:
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\SOFTWARE\Autodesk\AutoCAD\R18.0\ACAD-8001:409\Applications\NextPrev18\Groups]
"Support"="Support"
[HKEY_CURRENT_USER\SOFTWARE\Autodesk\AutoCAD\R18.0\ACAD-8001:409\Applications\NextPrev18]
"DESCRIPTION"="Next Previous Drawing in the Directory"
"LOADCTRLS"=dword:00000004
"LOADER"="C:\\Arch_Custom\\Support\\NextPrev18.dll"
"MANAGED"=dword:00000001
[HKEY_CURRENT_USER\SOFTWARE\Autodesk\AutoCAD\R18.0\ACAD-8001:409\Applications\NextPrev18\Commands]
"MyNext"="MyNext"
"MyPrevious"="MyPrevious"
Thanks again Tim. Works perfectly in version 2010.