No 'locked for editing' message for an Excel file on a network share

I get no 'locked for editing' message when accessing an Excel spreadsheet file on a network share (Windows SBS 2011 Standard) even though the file is open by a different user on a different workstation (Office 2013, Windows 8.1).

Is there any way of getting this fixed or should I just accept the fact that it won't work as intended?

We use Sophos, I've already tried excluding .xls files from real time scanning but the problem still persists.

Solution 1:

There's a possible answer at: https://helpdesk.yourofficeanywhere.co.uk/kb/a183/excel-loses-file-locked-for-editing-when-accessing-data-on-network-drive-mapped-via-group-policy.aspx

In summary: If the file is on a drive mapped by group policy, the periodic policy refresh can disconnect and reconnect the drive, causing the lock to vanish. You can change the action setting on the group policy from Replace to Update which should ensure that the connection doesn't get dropped.