Creating a Unique column a column of Duplicates

[Wulluby]

Hi,

I have a table with one column containing a lot of duplicates:
'Gantt Chart'!$A$8:$A$1000

I want to create a unique column in another sheet which I have done with:
=INDEX('Gantt Chart'!$A$8:$A$1000,MATCH(0,COUNTIF($AI$14:AI14,'Gantt Chart'!$A$8:$A$1000),0))

The issue I am having is that it has also pulled across headers. I can identify the data I want to pull across because in the column next to it, ('Gantt Chart'!$A$8:$A$1000), is a column containing a mix of text and data, (AAA001 for example).

Any pointers on how I incorporate a, 'only pull if there is contents in 'Gantt Chart'!$A$8:$A$1000' into the function,
=INDEX('Gantt Chart'!$A$8:$A$1000,MATCH(0,COUNTIF($AI$14:AI14,'Gantt Chart'!$A$8:$A$1000),0))

Thanks in advance.