Remote Working - help please

Hi, I'm looking to work a computer remotely. The computer is a monitoring machine in an office, I would like to be able to remotely work it about 40 metres away. It stiill needs to work in the office too! I am guessing I need a monitor, keyboard, mouse and some cabling - has anyone any ideas on what I could do to achieve this. I know there are distance issues and am just not sure what or how so would appreciate any help.

If it's a windows machine then you could use teamviewer or if not some other vnc software.