Protect Sheet option not available

[Dee]

I'm trying to protect my workbook because someone keeps
deleting formulas and i'm constantly fixing it. However
i've taken all the step to protect the cells and etc. and
when I try to "Protect Sheet" the option is not
highlighted for me to use. The only option available
is "Protect shared workbook".
I sent the same workbook to our IS department and they had
no problem with that option and it was available to use.
But it did not give me that option on my computer.
What is causing that and how can i fix it?
Thanks for your help.
Please email me.

 

[J.E. McGimpsey]

Is the workbook shared (Tools/Share Workbook..., or Tools/Track
Changes)?