how to xcopy or robocopy some files and keep original directory structure in tact

I I'm looking to write a batch file to backup needed files on a computer like pst, wab, dbx and the like files from arbitrary locations to an external drive, problem is, since there could be multiple outlook.pst files (diffrent profiles), I would like to keep the original directory structure, but only copy the needed files.

I looked through the needed switches using xcopy and robocpy but couldn't figure it out.  The only reason I think it can be done is that using one of these apps, I did it by mistake once.

Thanks for all your help.