Somehow, I lost formula bar, even I selected formular
bar in View menu and Preference.
Could you mention which version of Excel is concerned by
the issue you're describing, as the solution may differ?
You'll have to trash (or just rename, if you want to make
sure first) the "Excel Toolbars (9)" (or "Excel Toolbars
(10)" or "Excel Toolbars (11)", depending upon the version
you're using) to be found in your Preferences:Microsoft
Folder. Its corruption could be the cause.
If this doesn't help you out, post back with some more
indications.