I understand advanced filtering, but I've been trying to figure this
particular filter out for hours and it has me scratching my head (I think
because I'm having trouble using formulas in my filters).

What I'm trying to do is filter one column based on whether data in that
column is equal to data in another column. For example:

A B C D
1 10 12 14 10
2 10 11 15 15
3 12 12 14 12
4 11 15 10 11

Is there an easy way to filter where the data in column A equals the data in
column D? So using the above examples the filter would return rows 1, 3, and
4?

And a more complicated task, where data in column A equals the data in
column D, and is less than data in column C (which should return rows 1 and
4).

Any help is greatly appreciated!

Thanks,
-- gdmill