poppy,

For opening, do the following:

save the workbook with a password and a read only password. You keep
the password, and all other users only get the readonly password. This
way evereybody can open the sheet, but you can open and edit the sheet.
All at the same time.

Happy dreaming;) XL has no user level security control other that the
ones you program yourself. That said you can as standard hide the info
from your read only users, then your "super user" can still access the
data by lifting the protection and unhiding the hidden info.

BTW you can also start "sharing" a workbook, but that has it's own
repercussions.

DM Unseen