I have an IF statement based on 2 criteria in an OR statement.

.....IF a1=a2 or a1=a3, show a1 contents in a4....for instance.

I want to format a2 automatically depending on which of the 2 statements
about a1 turn out to be TRUE.

If a1=a2, show contents in a4 and make it bold text...if a1=a3, show
contents in a4, and make it italic text....for instance.

The problem is I can't use conditional formatting for the specific cells,
because the value in a4 is going to change depending on what I type in a2 and
a3.

Can anyone help?