Excel Formula Help

Hi, 

I'm hoping someone can help me. I'm desperaetly trying to work out a formula sort a script but just can't get it working.

I’m needing (if this makes sense) to be able to automatically input data from one sheet to another.

So for example: 

If column A (sheet one) matches anything  on column D (sheet 2). It copies the data from column I (sheet 1) to column A (sheet two) !!

Doe that make sense?? I'm desperate!