Creating a comma separated list from a column of numbers, omitting duplicates, spaces

Hello Excel forum community! I seek your expert advice again.

What I'm trying to do is take information that is located in a column of numbers, and be automatically forwarded to a single cell with commas between each number, and omitting any duplicates and spaces (empty cells), with them also being in numerical order.

For example:
8765
8765
9803
2011
8765
0008

in six columns would be taken to a single cell as:
0008, 2011, 8765, 9803


In the sample workbook attached, I have information in sheet two, column A and needs to be sent automatically as a comma'ed list to sheet one, B1

On sheet two, the space for potential data input is between A2 and A20

I can include my actual project (with dummy information) if the sample project doesn't explain clearly enough what I need to accomplish.

I only have limited knowledge of programing with VBA,so a code snippet would be preferred.

Thank you in advanced!