protect a cell from formating only but allow data incertion

I am trying to use a date feature to where you enter month in a field and it adds the days in other fields. that works but i need to be able to change a day field because i might need 2 of the same days for milage expenses. this works but i need to protect the field from formatting but then i can't change the day field manually. hope this is clear enough. it all works except when i double click on the day field it still allows formatting and I can't have that. any ideas. added link to file http://www.primenet.com/~azcaver/expenses.xls

• sample of expense sheet