counting formula

I need help, I can't seem to get a formula to work that will count a range of cells based of wether or not their value is greater than half the value in another column.

example:

200 300
210 440
40 550
320 500

i want to count 200 and 320 because they are more than half the values in column b.

I can't seem to get a countif or a dcount to work.

Just to count, i.e. to give a result of 2 for your example

=SUMPRODUCT(--(A1:A4>B1:B4/2))

Perfect, thanks.