Personally I would avoid the "can not save scenario". That tends to frustrate
users to no end. They close the file and loose their work and then call you
to complain. The prompt however is a good way to handle this, but it requres
a macro to make it happen. It is also helpful to have conditional formatting
of the cells in question to indicate which values are not within parameters.
Here is some sample code for you to test. To add this code right click the XL
logo next to the item File in the menu and select view Code. This prompts the
user when they try to close the file. You will need to change the sheet
reference and the range address...
Private Sub Workbook_BeforeClose(Cancel As Boolean)
If Sheets("Sheet1").Range("A1").Value > 100 Then
If MsgBox("Prameters exceeded. Did you still want to Exit?", _
vbCritical + vbYesNo, _
"Parameters Exceeded") = vbNo Then Cancel = True
End If
End Sub