you cant do it that way because only 1 instance of qb can be running on that computer which you are both using.
instead you would have to put the quickbooks data base on a third computer and both of you can select the database from that computer.
quickbooks used to have a cloud server that you could host your file on but they stopped that program in january to promote quickbooks online. Quickbooks online would solve your access problem but the program is nowhere near as robust as the desktop version and it does not do contracting stuff well.
there are basically 3 ways to do it.
1. a vpn line between the office and your home so that you can get into the quickbooks file hosted on their computer without logging into their computer.
In the long run this would probably be the best option for you as it allows you to join the network in the office from home and do other things such as print to the office computer and access anything on the network there.
2. a third computer that will host the qb file which you can log into using log me in while they access the file from a different computer.
3. a cloud hosting service that will hold the data file while you both log in from anywhere on the net.
This is one company that will do the hosting on the cloud for you. i dont know what they will charge for basically 2 man access. but it will be a monthly charge and might be easier than laying out the money to setup either of the other two options. there phone number is ***** the webpage