If left statement not working

Hello people,

I've been trying the following formula for hours and can't get it to work.

=IF(LEFT(D3,3)="INN","YES","NO")

Eventually I want it to sum up an entire column if the first three letters somewhere else in the row is INN.
Like this:
=IF(B:B;"CTBI"(SUM IF(LINKS(D:D,3="INN")))

The top formula should work, but it doesn't.

I'm using 2010 Plus Excel (Dutch version)

Any ideas are welcome,

Thanks

Hi Richard Buttrey,

Yes I'm looking for a sophisticated SUMIF that goes through a column and filters out which numbers I don't need by looking at 2 different columns.
That may not be possible, so I want that first formula to work so I can make a workaround formula.