Excel 2007 : Combine 2 cells containing text and eliminate duplicates

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Hey all, I could really use some help!! I'm struggling with how to combine multiple cells while parsing out duplicate data strings.

I have a spreadsheet where I am listing reference numbers in a certain column.

Each cell contains multiple reference numbers, and some reference numbers are listed in several cells.

I want to combine all of the reference numbers in all of the cells in to a single cell. I also do not want to list any duplicate reference numbers.

How can I combine the text in the cells while also eliminating any duplicate values? (See attachment for an example).

Any and all suggestions would be much appreciated!!!