Try in B55 copied across and down
=IF(B$54="",FALSE,IF(LEFT($A55,LEN(B$54)+1)=B$54&",", TRUE, IF(ISNUMBER(SEARCH(","&B$54&",",SUBSTITUTE($A55," ",""))),TRUE,FALSE)))
This can be shortened to
=OR((LEFT($A55,LEN(B$54)+1)=B$54&","),(ISNUMBER(SEARCH(","&B$54&",",SUBSTITUTE($A55," ","")))))
Does that work for you?
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