Prevent data being deleted after Enter & Save

I am creating a simple workbook with 4 possible entry categories; Date, Cash In, Cash Out, Comment.
What I need is to have the data automatically posted to the next blank line when entered, and not permit deletion. I need to do this to avoid any of the committee members trying to modify the books to help their wallets. Is there a simple way of doing this or am I looking at some complicated VBA?