5 of us are using a shared workbook. We all enter data in columns in
the next empty row, eg one entry consists of typing data into C10,
D10, E10, F10, G10 & H10. If user 1 & 2 both happen to be typing in
stuff on (say) row 10 and user 1 saves and then user 2 saves, user 2's
data overwites user 1's and user 1's data is lost.

Also I'm using a circular reference,
IF(C10="",""IF(B10="",NOW(),B10)), which puts the time of data entry
in B10 when C10 is filled. This works for the individual entry on the
PC of the user who made it, but, if another user saves, he gets the
time HE saved in C10 and (I'm assuming) that the last user of the day
to save would get the time HE saved on all other user's entries.

Any ideas?