INDEX MATCH with a COUNTIF for duplicates & CONCAT Function?

[pvtjoker77]

	R	S	T
51	HNL@internet.com	HNL		HNL@internet.com
52		SJC
53	OGG@internet.com	OGG		OGG@internet.com
54	HNL@internet.com	HNL

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I get the above results using the following formulas in U51:U56 And it removes the duplicate but how can I combine the non duplicate results from U51:U54 to have them them to look like
HNL@internet.com;OGG@internet.com? I know I have to use CONCAT function somehow.

End result is I would like to get them combined in any cell since I use it in a VBA that gets the email addresses from that cell to send and email

U51 =R51

U52 {=INDEX($R$51:$R$54, MATCH(0, COUNTIF($U$51:U51, $R$51:$R$54), 0))}

U53 {=INDEX($R$51:$R$54, MATCH(0, COUNTIF($U$51:U52, $R$51:$R$54), 0))}

U54 {=INDEX($R$51:$R$54, MATCH(0, COUNTIF($U$51:U53, $R$51:$R$54), 0))}

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