I would suggest that you would need to do a combination of 2 things.

1) Force users to use macros on your workbook.
There are plenty of other posts on here about how to do that, just search
for them; the general idea is to have one default sheet that comes up if
macros are not used, then all the other sheets in your workbook only get
unhidden if macros are switched on, and you do this within the workbook_open
event procedure.

2) Now that they are forced to use macros, use this code in the workbook
event procedure.

Private Sub Workbook_BeforeSave(ByVal SaveAsUI As Boolean, Cancel As Boolean)
  If SaveAsUI Then Cancel = True
End Sub

It stops them bringing up the Save As dialogue box.  More info on where to
put that code:
http://www.contextures.com/xlvba01.html#Workbook

Hi John,

You may want to look at Google Spreadsheets. Burgeoning technology
that I'm sure will become a part of many peoples corporate structure.

Just put 'google spreadsheets' into a google search and follow your nose.

HTH
Martin