When i beat it, I had one of my guys follow me and tried not to set off the alarm, but when I did, I ran to electrically locked door and left one guy there and then ran back to the remote lock place and opened the door and then switched to my other guy and went inside. I was able to complete the mission before time ran out. Theres probably a way you can do it without setting off the alarm but i don't know it. You might want to check the walkthrough at www.gamefaqs.com