Concatenation Function that separates values by comma and removes duplicates

I would like to start off by thanking you for your help with this. I am used Excel 2010 (PC) to aggregate the roles and responsibilities of our employees for a RACI exercise. I had our regional business managers fill in a template that indicated who performed a specific function (column Q) and the person who should be performing that function (column S). On a master template I used the following formula to aggregate all the responses:

=CONCATENATE(Dean!O17,Galvin!O17,'Josh Crosslin'!O17,DiMarco!O17,JES!O17,Schmidt!O17,Rosiello!O17,JJD!O17,AOC!O17,'R. Myers'!O17,'R. Myers 2'!O17,'R. Tesdall'!O17,'R. Tesdall 2'!O17,'T. Ponder'!O17,Doig!O17)

The names you see in the formula represent the individual tabs I created in the master template to reflect the results of the templates sent to the BMs. The result was:

CDM + Planning teamCDM + Planning teamCDMCDM + Planning teamCDM + Planning team

Is there a way I can modify this formula to show a result that is separated by commas and free of duplicates?

Thank you

You can't use a delimiter such as a comma with the concatenate function unless you were to do
=concatenate(Dean!O17,",",Gavin!O17,","... and so on.

Not sure how to go about removing duplicates though.

I tired that, but it yielded the following result:

,,,NCIM,Analytics/Insights Team,Insights + Local Teams,,AMG,AMG,,,Client and Strategic Team,Client and Strategic Team,Client and Planning Team,NCIM / CLIENT

Not sure why there were so many ,,,

Presumably some of the cells you reference are blank. I guess you could fix that with if() functions but the formula would quickly become unwieldy. Best bet might be a user defined function.

The ideal result from the formula in my original post is

CDM + Planning team, CDM

UDFs are not my specialty... I guess I need to work on that. Are there sites like codeacadmy.com where i can hone my VBA skills?

That worked for the excess commas, but do you have any suggestions on removing the duplicate values?

NCIM,CDM + Planning team,CDM + NCIM + Local Team,CIM,CIM,BIM,BIM,BIM,CDM / NCIM,

Thank you FDibbins