averaging formula

I currently have a formula which looks like this:

=AVERAGE(E9*D9,E10*D10,E11*D11,E12*D12,E13*D13,E14*D14,E15*D15,E16*D16,E17*D17,E18*D18)/AVERAGE(D9:D18)

Currently Cells E13,D13,E14,D14,E15,D15,E16,D16,E17,D17,E18,D18 are empty but would eventually become filled which is why i have included them in the average formula above. However it is obviously lowering the average because it is counting the cells that are empty as zero. I have been trying to use an IF FORMULA to correct this but as of yet have not managed it.

Am i pointing in the right direction, or perhaps someone could suggest an alternative formula.....thanks for your help!!!!