Hi. Can anyone help me, please??

I have a range of data on sheet 'Data'.
On another sheet, I have formula to count records that don't equal Y in
column F, and don't equal O in column G.
I have tried using an array formula.
{=SUM(IF(Data!F2:F20="<Y",IF(Data!G2:G20="<O",Da ta!D2:D20,0),0))}
I think this means that if the cell doesn't contain a Y, it looks to see if
the next column contains an O. If both values are true(not a Y or an O), then
the numbers in column D and added. If the values are false(either one of the
columns contains a Y or O) then the formula returns a zero.

However, it does not work as it keeps returning a zero, when I know it
should be returning a value.

Please help if you can. If you need any more info, just ask.
Thanks
Gem