Excel Tends to access network when I issue commands
 

Excel on my PC usually access network when I issue the first command (or
after stopping activities on Excel for a while).

My system will "freeze" and I see the LAN icon on system tray light up -
indicating the PC is communicating with the LAN server.

Is this due to some macro or other options that I have previously chosen ?
This sometimes happens when I am working on my powerpoint.

Can Excel and PowerPoint work properly without doing this "freeze" and
communicating with server ? It is taking up time and my patience !!