I'm almost embarrassed to ask this, so please no laughing...

Simple spreadsheet:
Column D - used to input the date in which an item sold. Left blank until item is sold.
Column E - contains the price we paid to purchase item.
Column F - contains the price we sold the item sold for.
Column G - I want this to show our profit (F-E), but only if there is a date in D.

This is what I have so far, but I keep getting FALSE:

=IF(ISBLANK(D6),IF(D6>0,F6-E6,0))

Please help! It's been quite some time since I have used Excel, but it's like riding a bike, right??