=MAX(IFNA(MATCH(REPT("D",ROW($1:$99)),RIGHT(A1,ROW($1:$99)),),))
=MATCH(1<0,MID(A1,LEN(A1)+1-ROW(INDIRECT("1:"&LEN(A1))),1)="D",)-1
=MAX(FREQUENCY(IF(MID(A1,ROW($1:$20),1)="D",ROW($1:$20)),IF(MID(A1,ROW($1:$20),1)<>"D",ROW($1:$20))))
=MAX(FREQUENCY(ROW($1:$20),IF(MID(A1,ROW($1:$20),1)<>"D",ROW($1:$20))))-1
=COUNT(FIND(REPT("D",ROW($1:$99)),A1)) |