you can use the NET USE command as mentioned, or you can map the shared folder and have the computer you called user1 logon at startup (that way the connection is established). this way the person on user1 shouldn't have to put in a password when accessing the file.
as for backing up a file, you can just create a batch file to simply copy the file over... here's hpw i would do it if this is what you were asking:
create a .txt file (with notepad) with the following line:
copy x:\folder\file_to_backup \\server\drive\folder
or
copy x:\folder\file_to_backup x:\folder
the first option would be used if the folder on the lan being copied to is not mapped.
replace x:\folder\file_to_backup with the location and file you are backing up
you might need to use short names such as c:\docume~1 to get to the documents and settings folder
the second option would be used if you mapped the shared lan folder and it has a drive letter on the computer user1
again, replace the generic terms withn the actual folder and filename
finally, save the file and change the extension from .txt to .bat
just double click the file to run it or you can use the windows task manager to schedule it to run at set times.
here is an example of a bat file i use to backup 3 excel files to 2 compiters on my lan and a backup drive on my computer:
copy c:\compum~1\*.xls \\K6-3\c\windows\desktop
copy c:\compum~1\*.xls \\E6gev\c\windows\desktop
copy c:\compum~1\*.xls g:\backup~1\SDbak