Vba code to conditionally format a specific range

I'm still a rookie at this and can readily use any help y'all can provide. I need to have some VBa code to do the following things:

1. Conditionally format a range - cells in "a" should be filled in red with white bold text when value is >20
(value of a is detrmined by subtracting the date in column b from the System date auto entered in c1)

2. Prevent the user from inserting/deleting rows from the Insert menu and from the right click menu

3. Allow users to insert rows that will be properly formatted by using a button (ax:hX) - they should also be able to delete a row (ax:hx).

I realize that this is a rather large request but I am hopeful that there is indeed a generous individual in the group willing to lend me his/her expertise.

Thank you

DummyBook2.xls