[Samba] Time out tuning ?

[Samba List Unetix]

Hello,

I have a samba server running at a customer site and they have the
follwing problem:
Employees of that company have for extended periods sometimes
word documents opened for editing, but it happens regularly that
for an half hour or more no activity takes place because they are
working on something else (it's a flower seed growing company , with pc's
in the glasshouses and they have to monitor the seedbeds and fill in 
now and then something in in word documents). When that happens
the word application returns a message that , "There was a sharing violation"
and "The data will be saved in a copy of the document" . This is very 
inconvenient, it's allso for sure that noone else opened the document while
they were busy doing something else , because these are all personal
records and noone else can access them.
Is this caused by a time out on the server? or the client? Is it possible
to configure the samba server to forcefully keep the connection between the
client and the server alive?

TIA
Wim Bakker