adding domain user to local Admin account while not connected to domain

HI
I have an user 12345 in INDIA domain. This user have allready a profile in Local system. Now I want to add this domain user account to local admin group. Currently I am travelling and not connected to domain. Earlier 12345 was the member of admin group in local system. But itspermission get removed due to some virus.
I have removed the virus .. Can I add this account to local admin with out connecting to domain.

Please advise ASAP.