Document or worksheet is protected?
If you mean worksheet you will need VBA to unprotect, spellcheck then
re-protect.
Sub Spell_Check()
ActiveSheet.Unprotect Password:="justme"
Cells.CheckSpelling SpellLang:=1033
ActiveSheet.Protect Password:="justme", DrawingObjects:=True, _
Contents:=True, Scenarios:=True
End Sub
Unprotects the sheet, does the spellcheck then reprotects the sheet.
"justme" can be changed to your password.
Gord Dibben MS Excel MVP