Cancel Conditional Formating if cell not empty

Hey all,
I am trying to have conditional formatting of cells apply only if another cell is blank in 2007.

A3 has a formatting of =MOD(ROW(),2)=1, then =AND(A3<>"",A3+15<=$G$1) to change the color based on date and finally =AND(A3<>"",A3+30<=$G$1) to again change the color again by date.

What I would like to do is for the cells in columb A to change only if corresponding columb B cell is empty, without using macros if possible.

How about editing the 2 And() conditions to include that codition?

e.g

=AND(A3<>"",B3="",A3+15<=$G$1)
=AND(A3<>"",B3="",A3+30<=$G$1)