I think that this prompt pops up before the workbook is opened--it's windows &
excel working together to see that the file is in use.

I don't think you can change this behavior.

You could let the other user open it and close it if the file was opened in
readonly mode, but sometimes it's very useful to be able to open in readonly
mode.

I wouldn't do this, but if you want, you can create a macro that does this
check:

Option Explicit
Sub auto_open()

With ThisWorkbook
If .ReadOnly = True Then
MsgBox "Opened in ReadOnly Mode--Closing!"
.close savechanges:=false
End If
End With

End Sub

(but if macros are disabled, then this won't help either.)

If you're new to macros, you may want to read David McRitchie's intro at:
http://www.mvps.org/dmcritchie/excel/getstarted.htm

macsaintly wrote:

When a spreadsheet is open by a user and a second user wishes to open it, is
it possible to remove the read only prompt that appears in the box that says
Read Only, Notify, Cancel? We wish it to be only viewed in any mode by one
exclusive user at a time but I cannot find an option to do this. I've tried
all the security settings etc.

--

Dave Peterson