Conditional concatenate……….
TEXTJOIN is a Excel 2016 new function.
Try this if you do not have this new function.
In E6, formula
=C6&IFERROR(INDEX(E7:E$25,INDEX(MATCH(TRUE,B7:INDEX(B7:B$25,IFERROR(INDEX(MATCH(TRUE,B7:B$25<>"",),),4))="",),)),)
and >> E6 >> Conditional Formatting >> choose Formula : =$B6="" >> format : select yellow color in Front and Fill >> OK
All Copy down
Regards
Bosco