Detect connection to a drive

Hi there,

I know it's possible to detect a connection to the internet, but what I
really need is to detect the connection to a particular networked drive.
What happens is that someone is updating a spreadsheet stored on the drive
and when they come to save it they get a message to say the connection has
been broken. If I could detect this earlier then it would save a lot of
wasted data entry.
Any ideas on a function to do this?

Many thanks in advance.