You can try out the below macro. If you are new to macros..
--Set the Security level to low/medium in (Tools|Macro|Security).
--From workbook launch VBE using short-key Alt+F11.
--From menu 'Insert' a module and paste the below code.
--Get back to Workbook.
--Run macro from Tools|Macro|Run <selected macro()>
Sub ProtectSheets()
Dim intCount As Integer
For intCount = 1 To 12
Sheets(CStr(MonthName(intCount, True))).Protect Password:="password"
Next
End Sub
Sub UnProtectSheets()
Dim intCount As Integer
For intCount = 1 To 12
Sheets(CStr(MonthName(intCount, True))).UnProtect Password:="password"
Next
End Sub